S-1/A

As filed with the Securities and Exchange Commission on April 20, 2012

Registration No. 333-170640

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

Amendment No. 10

TO

Form S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

KAYAK SOFTWARE CORPORATION

(Exact name of registrant as specified in its charter)

Delaware	4700	54-2139807
(State or other jurisdiction of incorporation or organization)	(Primary Standard Industrial Classification Code Number)	(I.R.S. Employer Identification Number)

55 North Water Street, Suite 1

Norwalk, CT 06854

(203) 899-3100

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Karen Ruzic Klein

General Counsel

55 North Water Street, Suite 1

Norwalk, CT 06854

(203) 899-3100

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Michael A. Conza
Bingham McCutchen LLP
One Federal Street
Boston, MA 02110
Tel: (617) 951-8000
Fax: (617) 951-8736 Richard D. Truesdell, Jr.
Davis Polk & Wardwell LLP
450 Lexington Ave.
New York, NY 10017
Tel: (212) 450-4000
Fax: (212) 701-5800

Approximate date of commencement of proposed sale to public: As soon as practicable after this Registration Statement is declared effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box.    ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier registration statement for the same offering.    ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier registration statement for the same offering.    ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer	¨		Accelerated filer	¨
Non-accelerated filer	x	(Do not check if a smaller reporting company)	Smaller reporting company	¨

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities to be Registered	Proposed Maximum Aggregate Offering Price(1)	Amount of Registration Fee(2)
Class A Common Stock, $0.001 par value per share	$50,000,000	$5,730

(1) Estimated solely for the purpose of calculating the registration fee pursuant to Rule 457(o) under the Securities Act of 1933. Includes the offering price attributable to shares available for purchase by the underwriters to cover over-allotments, if any.

(2) Previously paid.

The Registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Commission, acting pursuant to Section 8(a), may determine.

The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and we are not soliciting offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

PROSPECTUS (Subject to Completion)

Issued April 20, 2012

             SHARES

KAYAK Software Corporation

CLASS A COMMON STOCK

KAYAK Software Corporation is offering              shares of its Class A common stock. This is our initial public offering, and no public market exists for our shares. We anticipate that the initial public offering price will be between $              and $              per share.

Upon the completion of this offering, we will have two classes of authorized common stock, Class A common stock and Class B common stock. The rights of the holders of Class A common stock and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share. Each share of Class B common stock is entitled to ten votes per share and is convertible at any time into one share of Class A common stock. Upon completion of this offering, the holders of our Class B common stock shall be able to exercise not less than     % of the voting power of KAYAK Software Corporation.

Moreover, all shares of our common stock and preferred stock outstanding immediately prior to completion of this offering will automatically be converted into shares of our Class B common stock and all outstanding options and warrants exercisable for shares of our common stock and preferred stock will automatically become options and warrants exercisable for shares of our Class B common stock upon completion of this offering.

Concurrently with this offering we may issue additional shares of Class A common stock in private placements to certain existing stockholders. The number of shares issued in these private placements will depend on the initial public offering price. We will not pay any underwriting discounts or commissions on the shares issued in these concurrent private placements. See “Concurrent Private Placements.”

We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act and will therefore be subject to reduced reporting requirements.

We applied to list our Class A common stock on The NASDAQ Stock Market under the symbol “KYAK.”

Investing in our Class A common stock involves risks. See “Risk Factors” beginning on page 11.

PRICE $              A SHARE

	Price to Public	Underwriting Discounts and Commissions	Proceeds to Company
Per share	$	$	$
Total	$	$	$

KAYAK Software Corporation has granted the underwriters the right to purchase an additional              shares of Class A common stock to cover over-allotments.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares of Class A common stock to purchasers on                      , 2012.

MORGAN STANLEY DEUTSCHE BANK SECURITIES

PIPER JAFFRAY STIFEL NICOLAUS WEISEL PACIFIC CREST SECURITIES

                      , 2012

TABLE OF CONTENTS

	Page
Prospectus Summary		1
Risk Factors		11
Special Note Regarding Forward-Looking Statements		28
Use of Proceeds		30
Dividend Policy		30
Capitalization		31
Dilution		33
Selected Consolidated Financial and Operating Data		35
Management’s Discussion and Analysis of Financial Condition and Results of Operations		38
Business		58
Management		71

	Page
Executive Compensation		84
Certain Relationships and Related Party Transactions		104
Principal Stockholders		109
Description of Capital Stock		114
Material U.S. Federal Income Tax Considerations to Non-U.S. Holders		120
Shares Eligible for Future Sale		124
Underwriters		126
Concurrent Private Placements		131
Legal Matters		133
Experts		133
Where You Can Find Additional Information		133
Index to Consolidated Financial Statements		F-1

We have not authorized anyone to provide any information other than that contained or incorporated by reference in this prospectus or in any free writing prospectus prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We are offering to sell, and seeking offers to buy, shares of our Class A common stock only in jurisdictions where offers and sales are permitted. The information in this prospectus or any free-writing prospectus is accurate only as of its date, regardless of its time of delivery or of any sale of shares of our Class A common stock. Our business, financial condition, results of operations and prospects may have changed since that date.

Until                     , 2012 (25 days after the commencement of this offering), all dealers that buy, sell or trade shares of our Class A common stock, whether or not participating in this offering, may be required to deliver a prospectus. This delivery requirement is in addition to the obligation of dealers to deliver a prospectus when acting as underwriters and with respect to their unsold allotments or subscriptions.

For investors outside the U.S.: We have not and the underwriters have not done anything that would permit this offering, or possession or distribution of this prospectus, in any jurisdiction where action for that purpose is required, other than in the U.S. Persons outside the U.S. who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares of Class A common stock and the distribution of this prospectus outside of the U.S.

i

PROSPECTUS SUMMARY

This summary highlights information contained elsewhere in this prospectus and does not contain all of the information that you should consider in making your investment decision. Before investing in our Class A common stock, you should carefully read this entire prospectus, including our consolidated financial statements and the related notes and the information set forth under the headings “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” in each case included elsewhere in this prospectus. Some of the statements in this prospectus constitute forward-looking statements. See “Special Note Regarding Forward-Looking Statements” for more information.

KAYAK SOFTWARE CORPORATION

Overview

We are a technology-driven company committed to improving online travel. Cofounders of Expedia, Travelocity and Orbitz started KAYAK in 2004 to take a better approach to finding travel online. Our websites and mobile applications enable people to easily research and compare accurate and relevant information from hundreds of other travel websites in one comprehensive, fast and intuitive display. We also provide multiple filtering and sorting options, travel management tools and services such as flight status updates, pricing alerts and itinerary management. Once users find their desired flight, hotel or other travel products, KAYAK sends them to their preferred travel supplier or online travel agent website to complete their purchase, and in many cases, users may now complete hotel bookings directly through our websites and mobile applications.

KAYAK’s services are free for travelers. We offer travel suppliers and online travel agencies, or OTAs, an efficient channel to sell their products and services to a highly targeted audience focused on purchasing travel. We earn revenues by sending referrals to travel suppliers and OTAs and from a variety of advertising placements on our websites and mobile applications.

Since our commercial launch in 2005, KAYAK has experienced significant growth:

• For the year ended December 31, 2011, we generated $224.5 million of revenues, representing growth of 32% over the year ended December 31, 2010;

• For the year ended December 31, 2011, we generated income from operations of $14.3 million as compared to income from operations of $16.8 million for the year ended December 31, 2010. After adjusting for a $15.0 million impairment charge related to our decision to stop supporting the SideStep brand name, operating income for the year ended December 31, 2011 was $29.2 million, a 74% increase over the same period in 2010;

• For the year ended December 31, 2011, we had Adjusted EBITDA of $50.2 million representing growth of 56.2% over the year ended December 31, 2010. Adjusted Earnings Before Interest, Taxes, Depreciation and Amortization, or Adjusted EBITDA, is a non-generally accepted accounting principle metric used by management to measure our operating performance. See “—Summary Consolidated Historical Operating Data” for an additional description of Adjusted EBITDA and a reconciliation of Adjusted EBITDA to income (loss) from operations.

• For the year ended December 31, 2011, we processed 899 million user queries for travel information, representing growth of 42% over the year ended December 31, 2010; and

• KAYAK mobile applications have been downloaded over 13 million times since their introduction in March 2009. For the year ended December 31, 2011, we had 7 million downloads, representing growth of 78% over the year ended December 31, 2010.

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As of March 31, 2012, we had 169 employees, and we had local websites in 14 countries outside the U.S., including the United Kingdom, Germany, France, Spain, Italy and Austria.

Our Industry

Market Opportunity

As a distribution and advertising platform, we participate in both the online travel market and the online travel advertising market.

Online Travel: A Large and Growing Market. The travel industry in the U.S., Europe and Asia Pacific accounted for $803 billion in global expenditures in 2010, and is projected to increase at a 6% compound annual growth rate, or CAGR, through 2012. Of this amount, approximately $247 billion, or 31% was purchased online in 2010 representing a 16% CAGR between 2005 and 2010. We believe that travel, with its research and information intensive nature, real time pricing, electronic fulfillment capabilities and thousands of travel options, is well suited for the online channel. Currently, online travel represents the largest category of e-commerce, with total sales exceeding the combined total of electronics, books, software, appliances and collectibles.

Key Online Travel Products. The two largest categories of online travel are airline ticket sales and hotel bookings. In 2010, airline ticket sales represented 53% of total online travel purchases, followed by hotel bookings at 27%. Hotel bookings are the fastest growing online travel category and are projected to grow at an 11% CAGR from 2010 through 2012. Given the significant differentiation among hotels, travelers will typically spend considerable time online researching a hotel stay, making hotel bookings highly suitable for the online channel.

Online Travel Advertising: A Large Opportunity to Grow Share of Total Advertising Spend. Travel represents one of the largest advertising categories, with advertisers spending $31 billion globally on travel-related advertising in 2010. Of this amount, only $4 billion, or 14%, was spent online with the remainder being spent primarily on traditional media. We believe that travel advertising will continue to move from offline to online as travel purchases continue to move online. Online travel advertising can also be a more efficient advertising channel, as it enables advertisers to directly target individuals who are researching and planning travel. The online travel advertising market is expected to reach $9 billion by 2015, a CAGR of 15% between 2010 and 2015.

Challenges of Our Industry

Challenges for Consumers. Travel product pricing and availability change frequently, and information is often fragmented across hundreds of travel sites. Traditional travel websites can be slow and confusing and often lack comprehensive search results. These limitations can make it frustrating for people to find, purchase and manage their travel online. As a result, we believe that travelers continue to search multiple sites for the best prices and options to meet their travel needs.

Challenges for Travel Suppliers and OTAs. Travel suppliers and OTAs face two main challenges. One is to distribute their travel products to as many travelers as possible, while still maintaining their brand and owning the customer relationship. In distributing their travel inventory through third party sites, they lose the opportunity to cross sell or upsell additional products and to build brand loyalty. The second challenge they face is to advertise their services to the right audience at the right time, in a cost effective manner. The majority of travel advertising dollars is currently spent in offline media channels, including TV, radio, print and outdoor campaigns. Offline travel advertising can be expensive, and its effectiveness can be difficult to measure and track. Online advertising offers many improvements to traditional advertising, but can still suffer from audience fragmentation, generic advertising placements and complex pricing schemes.

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Our Strengths

We believe that KAYAK offers a better product for consumers, travel suppliers and OTAs.

KAYAK Provides a Fast, Intuitive and Comprehensive Travel Planning Experience. We use proprietary software and algorithms to quickly find, consolidate and sort travel information from hundreds of websites. We present these results through an intuitive interface, providing a single place for our users to plan their travel. Once a KAYAK user finds what they want to buy, we give them the flexibility to purchase directly from travel suppliers or OTAs, and in some cases, they can complete their bookings directly through our websites and mobile applications.

KAYAK is a Technology-Driven Company Focused on Rapid Innovation and the User Experience. We have invested significant time and resources building a technology platform that delivers the best user experience possible. The majority of our employees are either software engineers or technologists, and we believe we have one of the strongest technology teams in the travel industry. We strive to innovate faster than our competitors, and we release new code to our websites almost every week.

KAYAK’s Users are Loyal. We believe that our users are loyal to our brands, products and services. According to a June 2011 study conducted by a market research company on our behalf, KAYAK is a leading brand among the major online travel sites in the U.S. for attributes such as “Finds all the best prices in one place” and “Smarter way to search for travel online.” In 2011, 78% of our query volume was generated from people who directly visited our websites or used our mobile applications, and only 5% of our query volume was generated by users referred to us from general search engines.

KAYAK’s Proprietary Distribution and Advertising Platform is Optimized for the Travel Industry. We provide travel suppliers and OTAs with access to a valuable audience of people searching for travel information. Our query results include real-time pricing and availability information from travel suppliers and OTAs, from which a user can make a selection and be linked directly into the travel supplier’s or OTA’s purchase process, or in many cases, users may now complete hotel bookings directly through our websites and mobile applications. Our innovative platform allows advertisers to target their placements, create advertising content and link the user to the relevant page on the advertiser’s website, all based on the user’s query parameters.

KAYAK’s Unique Business Model is Highly Scalable. We designed our business model and technology platform to be highly scalable and cost efficient. Our software and systems have been designed from inception to handle significant growth in users and queries, without requiring significant re-engineering or major capital expenditures. In addition, we use a combination of our own proprietary software, public domain technologies and tiered pricing arrangements with third-party software providers so that as queries continue to grow, we do not incur proportionately higher software costs. Since all travel products are purchased by our users directly on the travel supplier’s or OTA’s website or through relationships with third party booking and fulfillment providers, we do not incur meaningful costs or overhead associated with fulfillment or customer service for those travel products. We have relatively low fixed operating costs, and the largest component of our variable operating cost is discretionary marketing.

The KAYAK Team Has Deep Industry Experience and Focus. Cofounders of Expedia, Travelocity and Orbitz formed KAYAK in 2004. Our team has extensive and longstanding relationships across the travel industry and, unlike general search engine companies, we focus on a single market category—online travel.

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Our Growth Strategy

Continue to Improve and Expand Our Services. We are dedicated to offering people the best online travel planning experience. We will continue to improve and expand our offerings, adding new travel suppliers and OTAs to our query results, improving our search algorithms to enhance the speed and relevance of our query results, making the booking path easier for travelers and adding new features to our websites and mobile applications.

Expand Our Booking Path Capabilities. We believe that many consumers would prefer to complete their bookings without having to leave our websites and mobile applications. In March 2011, we added the capability for consumers to make hotel reservations through our U.S. website. We have since introduced this feature to our mobile applications and across other geographies. Consumers benefit from a more seamless user experience, and we benefit from an increase in completed transactions. We intend to extend this capability to flights and rental cars.

Increase Consumer Awareness of Our Brands. We believe there is significant opportunity to increase the number of people who use our websites and mobile applications. In November 2009, we commenced a broad reach marketing program which resulted in our unaided awareness increasing to 31% for the month of January 2012 from 9% as of October 2009. We will continue to invest in broad reach marketing to increase our unaided awareness.

Grow Our Business Internationally. We recently opened an office in Zurich, Switzerland to serve as headquarters for our European operations. We operate websites in 14 countries outside of the U.S., including Germany, the United Kingdom, France, Spain, Italy and Austria. We believe that the international opportunity for our services is sizable, and we intend to continue to invest in both head count and marketing in 2012 and 2013.

Extend our Leadership Position in Mobile Applications. Mobile devices represent an important growth area in both audience and query volume. We have seen rapid adoption of our KAYAK mobile applications. We plan to extend our leadership position in travel-related mobile applications through continued product development to enhance the loyalty to our brand, products and services.

Risks Associated with Our Business

We are subject to a number of risks, including risks that may prevent us from achieving our business objectives or may adversely affect our business, financial condition, results of operations, cash flows and prospects. You should carefully consider these risks, including all of the risks discussed in the section entitled “Risk Factors,” beginning on page 11 of this prospectus, before investing in our Class A common stock. Risks relating to our business include, among others:

• we may be unable to maintain or establish relationships with travel suppliers and OTAs;

• if travel suppliers or OTAs choose not to advertise with us or choose to reduce or even eliminate the fees they pay us, our financial performance could be materially adversely affected;

• if we do not continue to innovate and provide tools and services that are useful to travelers, and if we are unable to retain or motivate key personnel or hire, retain and motivate qualified personnel we may not remain competitive, and our revenues and operating results could suffer;

• we primarily depend on a single third party to provide our airfare query results;

• competition from general search engine companies and other travel companies could adversely affect us;

• we may be unable to maintain and increase KAYAK brand awareness and preference;

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• we have limited international experience and may be limited in our ability to expand into international markets; and

• as a result of our dual class stock, our management and other affiliates will have significant control over our common stock and could control our actions in a manner that conflicts with the interests of other stockholders.

Corporate Information

Our principal executive offices are located at 55 North Water Street, Suite 1, Norwalk, CT 06854 and our telephone number at that address is (203) 899-3100. Our corporate website address is KAYAK.com. We do not incorporate the information contained on, or accessible through, our corporate website into this prospectus, and you should not consider it part of this prospectus. We were originally incorporated in Delaware in 2004 under the name Travel Search Company, Inc. We changed our name to Kayak Software Corporation in August 2004 and to KAYAK Software Corporation in December 2011.

Except where the context otherwise requires or where otherwise indicated, references herein to “KAYAK,” “we,” “our” and “us” refer to the operations of KAYAK Software Corporation and its consolidated subsidiaries. Our operations consist primarily of our flagship website KAYAK.com, which is part of a global family of websites that includes KAYAK.co.uk, swoodoo.com and checkfelix.com. We refer to these websites collectively as the KAYAK websites.

Market and Industry Data

Except as otherwise noted, all industry and market data in this prospectus were derived directly from data estimated and reported by PhoCusWright Inc. (PhoCusWright) or International Data Corporation (IDC), or were estimated by us using such data as the primary source. Industry publications, studies and surveys generally state that they have been prepared from sources believed to be reliable, although they do not guarantee the accuracy or completeness of such information. While we believe that each of these studies and publications is reliable, we have not independently verified such data, or any other industry or market data from third-party sources referenced in this prospectus.

Trademarks

KAYAK^®, swoodoo^TM, checkfelix.com^® and Search One and Done^® are our key trademarks and are registered under applicable intellectual property laws. This prospectus contains references to our trademarks and service marks and to those belonging to other entities. Solely for convenience, trademarks and trade names referred to in this prospectus, including logos, artwork and other visual displays, may appear without the ^® or ^TM symbols, but such references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or the rights of the applicable licensor to these trademarks and trade names. We do not intend our use or display of other companies’ trade names, trademarks or service marks to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

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THE OFFERING

Class A common stock offered by KAYAK Software Corporation	shares
Total Class A common stock to be outstanding after this offering	shares
Total Class B common stock to be outstanding after this offering	shares
Total common stock outstanding after this offering	shares
Concurrent Private Placements	Upon the closing of this offering, certain of our existing stockholders will have the right to purchase from us up to an aggregate of $9.2 million of Class A common stock, at the initial public offering price, in a concurrent private placement. Based on an assumed initial public offering price of $             per share, which is the midpoint of the range set forth on the cover of the prospectus, such stockholders will have the right to purchase from us up to an aggregate of              shares of Class A common stock. This right must be exercised, if at all, within five business days of the date on which we consummate the initial public offering, and will not apply if the initial public offering price per share equals or exceeds $31.09 per share. We have also agreed that we will issue, without further consideration, additional shares of Class A common stock to certain of our existing stockholders if our initial public offering price is less than $27.00 per share. In that event, the total number of such additional shares will be calculated by taking the amount by which $27.00 exceeds the initial public offering price per share, dividing that excess amount by the initial public offering price per share and, finally, multiplying the result by             , which is the number of shares of Series D preferred stock held by the stockholders entitled to the automatic adjustment. Based on an assumed initial public offering price of $             per share, which is the midpoint of the range set forth on the cover of the prospectus, we will issue to such stockholders, for no additional consideration,              additional shares of our Class A common stock. Any increase or decrease in the assumed initial public offering price of $             per share would decrease or increase, respectively, the aggregate number of shares that may be issued in these concurrent private placements. See “Concurrent Private Placements.”

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	We will not pay any underwriting discounts or commissions on the shares issued in these concurrent private placements.
Voting rights	The holders of Class A common stock generally have rights, including as to dividends, identical to those of holders of Class B common stock, except that holders of Class A common stock are entitled to one vote per share, representing in the aggregate             % of the combined voting power of all classes of voting stock, and holders of Class B common stock are generally entitled to ten votes per share, representing in the aggregate             % of the combined voting power of all classes of voting stock. Holders of the Class A common stock and the Class B common stock generally vote together as a single class, except when amending or altering any provision of our amended and restated certificate of incorporation or by-laws so as to adversely affect the rights of one class. See “Description of Capital Stock—Common Stock—Voting Rights.” The Class B common stock may be converted into Class A common stock at the option of the holder at any time and shall convert automatically upon certain specified transfers. See “Description of Capital Stock—Common Stock—Conversion.”
Use of proceeds	While we do not have any current specific plans for the net proceeds resulting from this offering, we expect to use the net proceeds from this offering for working capital and other general corporate purposes. We may also use a portion of the proceeds to expand our current business through acquisitions or investments in other strategic businesses, products or technologies. We have no commitments with respect to any such acquisitions or investments at this time.
Risk Factors	See “Risk Factors” for a discussion of factors that you should consider carefully before deciding whether to purchase shares of our Class A common stock.
Proposed NASDAQ Stock Market symbol	KYAK.

7

Except as otherwise indicated, all information in this prospectus:

• assumes no exercise of the underwriters’ over-allotment option;

• assumes the conversion of all outstanding shares of our common stock, Series A convertible preferred stock, Series A-1 convertible preferred stock, Series B convertible preferred stock, Series B-1 convertible preferred stock, Series C convertible preferred stock and Series D convertible preferred stock, collectively, our convertible preferred stock, into an aggregate of 33,793,123 shares of our Class B common stock and conversion of all outstanding options and warrants into options and warrants to purchase an aggregate of 9,190,490 shares of our Class B common stock; such conversions of preferred stock and preferred stock warrants will occur upon completion of this offering in accordance with the pre-existing terms of our convertible preferred stock and preferred stock warrants, and we will not be repurchasing any of such outstanding shares in connection with this offering;

• assumes the issuance of              shares of Class A common stock to certain existing stockholders pursuant to the automatic adjustment described under “Concurrent Private Placements,” based on an assumed initial public offering price of $             per share, which is the midpoint of the range set forth on the cover of the prospectus;

• assumes an initial public offering price of $             per share, the midpoint of the initial public offering price range indicated on the cover of this prospectus;

• excludes 103,904 shares of Class B common stock issuable upon the exercise of warrants outstanding as of December 31, 2011 with a weighted average exercise price of $13.57 per share;

• excludes 9,086,586 shares of Class B common stock issuable upon the exercise of options outstanding as of December 31, 2011 with a weighted average exercise price of $10.79 per share; 

• excludes 159,946 shares of Class B common stock reserved for issuance pursuant to future grants of awards under our Third Amended and Restated 2005 Equity Incentive Plan as of December 31, 2011;

• excludes the issuance of              shares of common stock reserved for future grants of awards under the 2012 Equity Incentive Plan as of the date of this prospectus; and

• excludes the issuance of              shares of Class A common stock pursuant to the private placement purchase rights described under “Concurrent Private Placements,” based on our assumed initial public offering price of $         per share, which is the midpoint of the range set forth on the cover of the prospectus.

Unless indicated otherwise all references to “common stock” for periods after completion of this offering refer to our Class A common stock and Class B common stock on an aggregate basis.

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SUMMARY CONSOLIDATED HISTORICAL AND OPERATING DATA

The following summaries of our consolidated financial and operating data for the periods presented should be read in conjunction with “Selected Consolidated Financial and Operating Data,” “Capitalization,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and the related notes included elsewhere in this prospectus. The summary consolidated statements of operations data for the years ended December 31, 2009, 2010, and 2011, have been derived from our audited financial statements included elsewhere in this prospectus. The historical results presented below are not necessarily indicative of the results to be expected for any future period.

	Years ended December 31,
Consolidated Statements of Operating Data:	2009			2010			2011
(in thousands except share and per share amounts)
Revenues	$	112,698		$	170,698		$	224,534
Cost of revenues (excludes depreciation and amortization)		15,362			15,630			18,598
Selling, general and administrative expenses:
Marketing		57,389			91,721			111,018
Personnel		22,638			29,764			40,785
Other general and administrative expenses		6,568			9,967			16,400
Total selling, general and administrative expenses (excludes depreciation and amortization)		86,595			131,452			168,203
Depreciation and amortization		5,380			6,821			8,486
Impairment of intangible assets(1)		—			—			14,980
Income from operations		5,361			16,795			14,267
Other income (expense)		(1,225	)		3,357			2,115
Income tax expense (benefit)		(2,776	)		12,120			6,681
Net income	$	6,912		$	8,032		$	9,701
Net loss per common share (after redeemable convertible preferred stock dividends)
Basic	$	(0.92	)	$	(0.57	)	$	(0.28	)
Diluted	$	(0.92	)	$	(0.57	)	$	(0.28	)
Weighted average shares outstanding:
Basic		5,223,187			6,463,639			7,309,202
Diluted		5,223,187			6,463,639			7,309,202
Unaudited pro forma:(2)
Net income per common share:
Basic							$	0.28
Diluted							$	0.26
Weighted average common shares:
Basic								34,076,858
Diluted								37,740,386
Other Data:
Adjusted EBITDA (3)	$	16,188		$	32,119		$	50,160
Capital expenditures	$	2,269		$	2,273		$	4,260
Queries (4)		458,594			634,319			898,573

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Consolidated Balance Sheet Data:
	December 31, 2011			Pro Forma at December 31, 2011(2)		Pro Forma as  Adjusted(5)
	(unaudited)
Cash and cash equivalents	$	35,127		$	35,127
Working capital		65,560			65,560
Total assets		277,948			277,948
Total liabilities		32,178			32,178
Redeemable convertible preferred stock		247,494			—
Total stockholders’ (deficit) equity		(1,724	)		245,770

(1) In January 2011, we determined that we would not support two brand names and URLs in the United States and decided that we would migrate all traffic from sidestep.com to KAYAK.com. As a result, our SideStep brand name and URL intangible assets were impaired, and we incurred a related write-down of $15.0 million in the first three months of 2011.

(2) The pro forma balances give effect to the conversion of all outstanding shares of our common stock and our redeemable convertible preferred stock into 33,793,123 shares of our Class B common stock.

(3) Earnings Before Interest, Taxes, Depreciation and Amortization, or EBITDA, is a metric used by management to measure operating performance. Adjusted EBITDA represents EBITDA excluding the impact of stock-based compensation expense and other income (expense), net. We present Adjusted EBITDA as a supplemental performance measure because we believe it facilitates operating performance comparisons from period to period and company to company by backing out potential differences caused by variations in capital structures (affecting other income (expense), net), tax positions (such as the impact on periods or companies of changes in effective tax rates), the age and book depreciation of fixed assets (affecting relative depreciation expense), the impact of acquisitions and the impact of stock-based compensation expense. Because Adjusted EBITDA facilitates internal comparisons of operating performance on a more consistent basis, we also use Adjusted EBITDA in measuring our performance relative to that of our competitors. Adjusted EBITDA is not a measurement of our financial performance under GAAP and should not be considered as an alternative to net income, operating income or any other performance measures derived in accordance with GAAP or as an alternative to cash flow from operating activities as a measure of our profitability or liquidity. We understand that although Adjusted EBITDA is frequently used by securities analysts, lenders and others in their evaluation of companies, Adjusted EBITDA has limitations as an analytical tool, and you should not consider it in isolation, or as a substitute for analysis of our results as reported under GAAP. Some of these limitations are:

• Adjusted EBITDA does not reflect our cash expenditures or future requirements for capital expenditures or contractual commitments;

• Adjusted EBITDA does not reflect changes in, or cash requirements for, our working capital needs;

• although depreciation is a non-cash charge, the assets being depreciated will often have to be replaced in the future, and Adjusted EBITDA does not reflect any cash requirements for such replacements; and

• other companies in our industry may calculate Adjusted EBITDA differently than we do, limiting its usefulness as a comparative measure.

The following table reconciles income (loss) from operations to Adjusted EBITDA for the periods presented and is unaudited:

	Years ended December 31,
	2009			2010			2011
Income from operations	$	5,361		$	16,795		$	14,267
Other income (expense), net		(1,346	)		3,250			2,004
Depreciation and amortization		5,380			6,821			8,486
Impairment of intangible assets(1)		—			—			14,980
EBITDA		9,395			26,866			39,737
Stock-based compensation expense		5,447			8,503			12,427
Other (income) expense, net		1,346			(3,250	)		(2,004	)
Adjusted EBITDA	$	16,188		$	32,119		$	50,160

(4) Queries refer to user requests for travel information we process through our websites and mobile applications.

(5) Pro forma as adjusted basis reflects: (i) pro forma basis conversions as described above, (ii) the sale by us of                  shares of Class A common stock in this offering and our receipt of the estimated net proceeds from that sale, based on an assumed public offering price of $             per share, which is the midpoint of the range set forth on the cover page of this prospectus, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us and (iii) the filing of our restated certificate of incorporation which will occur prior to the closing of this offering.

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RISK FACTORS

Risks Related to Our Business and Industry

We may be unable to maintain or establish relationships with travel suppliers and OTAs, which could limit the information we are able to provide to travelers.

Our ability to attract travelers to our websites and use our mobile applications and our services depends in large part on providing a comprehensive set of query results. To do so, we maintain relationships with travel suppliers and OTAs to include their data in our query results. The loss of existing relationships with travel suppliers or OTAs, or an inability to continue to add new ones, may cause our query results to provide incomplete pricing, availability and other information important to travelers using our services. This deficiency could reduce traveler confidence in the query results we provide, making us less popular with travelers.

With respect to our flight and fare information, the willingness of airlines to participate in our query results can vary by carrier. Historically, Southwest Airlines has chosen not to include its pricing and availability information in our query results and those of other third parties. If we are unable to continue to display travel data from multiple airline carriers, it would reduce the breadth of our query results and the number of travelers using our services could decline, resulting in a loss of revenues and a decline in our operating results.

Recently, there has been an increase in domestic airline consolidation, including the 2008 merger between Delta Air Lines and Northwest Airlines, the 2010 merger between United Airlines and Continental Airlines and the 2011 merger of AirTran Airlines and Southwest Airlines. If one of our airline travel suppliers merges or consolidates with, or is acquired by, another company with which we do not have a relationship, we may lose that airline as a participant in our query results or as an advertiser. We could also lose an airline’s participation in the event of an airline bankruptcy.

Approximately 10% of the hotels displayed on our websites are comprised of five hotel chains. A loss of any one of these brand name hotel chains as a travel supplier, or a loss of any one of these chains as a provider of travel information to OTAs, could have a negative impact on our business, results of operations and financial condition.

In addition, many of our agreements with travel suppliers and OTAs are short-term agreements that may be terminated on 30 days’ notice. We cannot guarantee that travel suppliers and OTAs will continue to work with us. We may also be unable to negotiate access, pricing or other terms that are consistent or more favorable than our current terms. A failure to retain current terms or obtain more favorable terms with our travel suppliers and OTAs could harm our business and operating results.

If travel suppliers or OTAs choose not to advertise with us, or choose to reduce or even eliminate the fees they pay us, our financial performance could be materially adversely affected.

Our current financial model depends almost entirely on fees paid by travel suppliers and OTAs for referrals from our query results and advertising placements. Since we do not have long-term contracts with most of the travel suppliers or OTAs who use our services, these travel suppliers or OTAs could choose to modify or discontinue their relationship with us with little to no advance notice to us. These changes may include a cessation in the provision of travel data to us, or a reduction in, or elimination of, our compensation.

During the year ended December 31, 2011, our top ten travel suppliers and OTAs accounted for approximately 61% of our total revenues. In particular, for the year ended December 31, 2011, Expedia and its affiliates, including its Hotels.com and Hotwire subsidiaries, accounted for 24% of our total revenues. Also during this period, Orbitz and its affiliates, including its CheapTickets, HotelClub and ebookers subsidiaries, accounted for 12% of our total revenues. If our relationship with any of our top travel suppliers or OTAs were to end or otherwise be materially reduced, our revenues and operating results could experience significant decline.

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If we do not continue to innovate and provide tools and services that are useful to travelers, we may not remain competitive, and our revenues and operating results could suffer.

Our success depends on continued innovation to provide features and services that make our websites and mobile applications useful for travelers. Our competitors are constantly developing innovations in online travel-related services and features. As a result, we must continue to invest significant resources in research and development in order to continually improve the speed, accuracy and comprehensiveness of our services. If we are unable to continue offering innovative products and services, we may be unable to attract additional users or retain our current users, which could adversely affect our business, results of operations and financial condition.

We primarily depend on a single third party to provide our airfare query results, and a loss of this provider could limit our ability, or make it more difficult for us, to provide travelers with accurate flight information.

We license faring engine software from ITA Software, Inc., or ITA, under an agreement which expires on December 31, 2013. This faring engine software directly provided approximately 41% of our overall airfare query results for the three months ended March 31, 2012. Additionally, 17% of our overall airfare query results during such period were obtained from other sources which, in turn, utilized the ITA faring engine software. We have invested significant time and resources to develop proprietary software and practices to optimize the output from ITA’s software for our websites and mobile applications. In addition, we believe that alternative faring engine solutions currently do not provide the level of comprehensiveness and accuracy that ITA’s software provides.

Airline travel queries accounted for approximately 86% of the queries performed on our websites and mobile applications for the three months ended March 31, 2012, and distribution revenues from airline queries represented approximately 25% of our revenues for the year ended December 31, 2011. We anticipate domestic airfare queries will continue to represent a significant portion of our overall queries for the foreseeable future. Thus, a loss of access to ITA’s software or enhancements or improvements to the software, or an adverse change in our costs associated with use of the ITA software, could have a significant negative effect on the comprehensiveness and/or speed of our query results, and on our revenues and operating results. Moreover, we believe that a significant number of travelers who use our websites and mobile applications for our non-air travel services first come to our site to conduct queries for airfare, and accordingly a loss, disruption or other negative impact on our airfare query results could also result in a significant decline in the use of, and financial performance of, our query services for non-air travel queries.

In the event we are not offered access to Google’s enhancements of or replacements to ITA software at competitive prices or at all, our ability to compete and operate our business effectively, and our financial performance, may be materially adversely affected.

On April 8, 2011, Google, Inc., or Google, entered into a consent decree agreeing to conditions on Google’s acquisition of ITA, and Google subsequently completed its acquisition of ITA. The consent decree stated Google’s intent to offer an online travel search product and Google has since launched hotel and flight search tools and services that directly compete with the tools and services we offer. Google’s flight search offering includes significantly increased speed on return of search results and, in the future, may include other enhancements or improvements in performance of the ITA software which may not be made available to us. Although the consent decree will provide us with the right to renew our existing ITA agreement on the same terms until October 2016, if ITA or Google limit our access to the ITA software or any improvements to the software, separately develop replacement software to which they claim we are not entitled or increase the price we pay for any improvements or replacement software and we are unable to replace ITA’s software with a comparable technology, we may be unable to operate our business effectively and our financial performance may suffer.

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Competition from general search engine companies could adversely affect us by reducing traffic to our website and mobile applications and by creating a competitive product that people choose over KAYAK when searching for travel online.

Large, established Internet search engines with substantial resources and expertise in developing online commerce and facilitating Internet traffic are creating, and are expected to create further, inroads into online travel, both in the U.S. and internationally. For example, in addition to its acquisition of ITA, Google has launched a travel search offering that displays hotel and airfare information and rates to travelers. Moreover, Microsoft acquired one of our competitors, Farecast.com, in 2008 and relaunched it as Bing Travel, a travel search engine which not only allows users to search for airfare and hotel reservations but also purports to predict the best time to purchase. These initiatives appear to represent a clear intention by Google and Microsoft to appeal more directly to travel consumers and travel suppliers by providing more specific travel-related search results, which could lead to more travelers using services offered by Google or Bing instead of those offered on our websites and mobile applications. For example, Google has launched the ability for users of its website to search for hotel and airfare pricing and availability, and as Google integrates such offerings with other Google services such as Google maps and weather information, then the number of users that visit our websites and our ability to attract advertising dollars could be negatively impacted. According to Experian Hitwise, in September 2010, approximately 30% of traffic to travel-related websites began with Google. Google or other leading search engines could choose to direct general searches on their respective websites to their own travel search service and/or materially improve search speed through hardware investments, which also could negatively impact the number of users that visit our websites and our ability to attract advertising dollars. If Google or other leading search engines are successful in offering services that directly compete with ours, we could lose traffic to our websites and mobile applications, which could have a material adverse effect on our business, results of operations and financial condition.

We may be unable to maintain and increase brand awareness and preference, which could limit our ability to maintain our current financial performance or achieve additional growth.

We rely heavily on the KAYAK brand. In our international markets we also rely on swoodoo and our other brands. Awareness, perceived quality and perceived differentiated attributes of our brands are important aspects of our efforts to attract and expand the number of travelers who use our websites and mobile applications. Since many of our competitors have more resources than we do, and can spend more advertising their brands and services, we are required to spend considerable money and other resources to preserve and increase our brand awareness. Should the competition for top-of-mind awareness and brand preference increase among online travel services, we may not be able to successfully maintain or enhance the strength of our brand. Even if we are successful in our branding efforts, such efforts may not be cost effective. If we are unable to maintain or enhance traveler and advertiser awareness of our brand cost effectively, our business, results of operations and financial condition would be adversely affected.

In November 2009, we began a broad-reach marketing campaign that included television commercials and signage advertising in major U.S. airports. We do not know if continued marketing investments will result in new or additional travelers visiting our websites or using our mobile applications. If we are unable to recover these additional costs through an increase in the number of travelers using our services, or if we discontinue our broad-reach campaign, we will likely experience a decline in our financial results.

We have registered domain names for websites that we use in our business, such as KAYAK.com, KAYAK.co.uk, swoodoo.com and checkfelix.com. If we lose the ability to use a domain name, we would be forced to incur significant expenses to market our services under a new domain name, which could substantially harm our business. In addition, our competitors could attempt to capitalize on our brand recognition by using domain names similar to ours. Domain names similar to ours have been registered in the U.S. and elsewhere, and in some countries the top level domain name “KAYAK” is owned by other parties. We may be unable to prevent third parties from acquiring and using domain names that infringe on, are similar to, or otherwise decrease the

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value of, our brand or our trademarks or service marks. Protecting and enforcing our rights in our domain names and determining the rights of others may require litigation, which could result in substantial costs and diversion of management attention.

Competition from other travel companies could result in a decrease in the amount and types of travel information we display, a loss of travelers using our products and services and a decrease in our financial performance.

We operate in the highly competitive online travel category. Many of our current and potential competitors, including general search engines, OTAs, travel supplier websites and other travel websites, have existed longer and have larger customer bases, greater brand recognition and significantly greater financial, marketing, personnel, technical and other resources than KAYAK. Some of these competitors may be able to secure services on more favorable terms. In addition, many of these competitors may be able to devote significantly greater resources to:

• marketing and promotional campaigns;

• attracting and retaining key employees;

• securing participation of travel suppliers and access to travel information, including proprietary or exclusive content;

• website and systems development; and

• enhancing the speed at which their services return user search results.

In addition, consolidation of travel suppliers and OTAs could limit the comprehensiveness of our query results and the need for our services and could result in advertisers terminating their relationships with us.

Increased competition could result in reduced operating margins and loss of market share. There can be no assurance that we will be able to compete successfully against current and future competitors or that competition will not have a material adverse effect on our business, results of operations and financial condition.

Changes in general search engine algorithms and dynamics or termination of traffic-generating arrangements could result in a decrease in the number of people directed to our websites.

We use Internet search engines, principally through the purchase of travel-related keywords, to generate traffic to our websites. The purchase of travel-related keywords consists of anticipating what words and terms consumers will use to search for travel on general search engines and then bidding on those words and terms in the applicable search engine’s auction system. We bid against other advertisers for preferred placement on the applicable general search engine’s results page. Approximately 5% of our user queries during the year ended December 31, 2011 resulted from searches initially entered on general search engine websites. Search engines, such as Google, frequently update and change the logic which determines the placement and ordering of results of a user’s search, which may reduce the effectiveness of the keywords we have purchased. If a major search engine, such as Google, changes its algorithms in a manner that negatively affects the search engine ranking of our websites, or changes its pricing, operating or competitive dynamics to our disadvantage, our business, results of operations and financial condition could be adversely affected. We also rely to a certain extent on advertisements that we place on other travel search engines. Approximately 6% of our user queries during the year ended December 31, 2011 resulted from these traffic-generating arrangements. A loss of one or more of these traffic-generating arrangements as an advertising channel could result in fewer people using our services.

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We have limited international experience and may be limited in our ability to expand into international markets, which could result in significant costs to us and a limitation on our ability to achieve future financial growth.

We operate websites in 14 countries outside of the U.S., and we generated approximately 18% of our net revenues for the year ended December 31, 2011 from our international operations. With the exception of our managing director for Europe, our senior management team is located in the U.S. and has limited international experience. We believe that international expansion will be important to our future growth, and therefore we currently expect that our international operations will increase. As our international operations expand, we will face increasing risks resulting from operations in multiple countries, including:

• differences and unexpected changes in regulatory requirements and exposure to local economic conditions;

• limits on our ability to enforce our intellectual property rights;

• restrictions on the repatriation of non-U.S. investments and earnings back to the U.S., including withholding taxes imposed by certain foreign jurisdictions;

• requirements to comply with a number of U.S. and international regulations, including the Foreign Corrupt Practices Act;

• uncertainty over our ability to legally enforce our contractual rights; and

• currency exchange rate fluctuations.

To the extent we are not able to effectively mitigate or eliminate these risks, our results of operations could be adversely affected. Furthermore, any failure by us to adopt appropriate compliance procedures to ensure that our employees and agents comply with applicable laws and regulations in foreign jurisdictions could result in substantial penalties or restrictions on our ability to conduct business in certain foreign jurisdictions.

Some of our plans for expansion include operating in international markets where we have limited operating experience. These markets may have different competitive conditions, traveler preferences and discretionary spending patterns than the U.S. travel market. As a result, our international operations may be less successful than our U.S. operations. Travelers in other countries may not be familiar with our brands, and we may need to build brand awareness in such countries through greater investments in advertising and promotional activity than we originally planned. In addition, we may find it difficult to effectively hire, manage, motivate and retain qualified employees who share our corporate culture. We may also have difficulty entering into new agreements with foreign travel suppliers and OTAs on economically favorable terms.

Our failure to manage growth effectively could harm our ability to attract and retain key personnel and adversely impact our operating results.

Our culture is important to us. We believe it has been a major contributor to our success. As we grow, however, we may have difficulty maintaining our culture or adapting it sufficiently to meet the needs of our operations. Failure to maintain our culture could negatively impact our operations and business results.

We have rapidly and significantly expanded our operations and anticipate expanding further to pursue our growth strategy. Our workforce worldwide has grown from fewer than 35 employees in 2006 to 169 employees and approximately 49 contractors as of March 31, 2012. Such expansion increases the complexity of our business and places a significant strain on our management, operations, technical performance, financial resources and internal control over financial reporting functions.

There can be no assurance that we will be able to manage our expansion effectively. Our current and planned personnel, systems, procedures and controls may not be adequate to support and effectively manage our future operations, especially as we employ personnel in multiple geographic locations. We may not be able to hire, train, retain, motivate and manage required personnel, which may limit our growth, damage our reputation and negatively affect our financial performance and harm our business.

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We may not be able to expand our business model beyond providing travelers with travel query results and our attempts to do so could result in significant additional costs to us without a corresponding increase in our revenues.

We plan to expand our business model beyond helping travelers search for travel by offering additional services and tools, including assisted booking services through mobile applications and our websites. This growth strategy depends on various factors, including the willingness of travel suppliers and OTAs to participate in our assisted booking services, as well as travelers’ use of these other new services and a willingness to trust us with their personal information. These newly launched services may not succeed, and, even if we are successful, our revenues may not increase. These new services could also increase our operating costs and result in costs that we have not incurred in the past, including customer service.

We are dependent on the leisure travel industry and declines in leisure travel or discretionary spending generally could reduce the demand for our services.

Our financial prospects are significantly dependent upon leisure travelers using our services. Leisure travel, including leisure airline tickets, hotel room reservations and rental car reservations, is dependent on personal discretionary spending levels. Leisure travel services tend to decline, along with the advertising dollars spent by travel suppliers, during general economic downturns and recessions. The current worldwide economic conditions have led to a general decrease in leisure travel and travel spending, which has negatively impacted the demand for our services.

Events beyond our control also may adversely affect the leisure travel industry, with a corresponding negative impact on our business and results of operations. Natural disasters, including hurricanes, tsunamis, earthquakes or volcanic eruptions, as well as other natural phenomena, such as outbreaks of H1N1 influenza (swine flu), avian flu and other pandemics and epidemics, have disrupted normal leisure travel patterns and levels. The leisure travel industry is also sensitive to other events beyond our control, such as work stoppages or labor unrest at any of the major airlines, political instability, regional hostilities, increases in fuel prices, imposition of taxes or surcharges by regulatory authorities, travel related accidents and terrorist attacks, any of which could have an impact on our business and results of operations. Although the September 2001 terrorist attacks in the U.S. occurred before we were formed, those attacks had a dramatic and sustained impact on the leisure travel industry, and any future terrorist attack, whether on a small or large scale, could have a material and negative impact on our business and results of operations.

We rely on the performance of highly skilled personnel, including senior management and our technology professionals, and if we are unable to retain or motivate key personnel or hire, retain and motivate qualified personnel, our business would be harmed.

We believe our success has depended, and continues to depend, on the efforts and talents of our senior management and our highly skilled team members, including our software engineers. Our future success depends on our continuing ability to attract, develop, motivate and retain highly qualified and skilled employees. The loss of any of our senior management or key employees could materially adversely affect our ability to build on the efforts they have undertaken and to execute our business plan, and we may not be able to find adequate replacements. In particular, the contributions of certain key senior management in the U.S. are critical to our overall success. We cannot ensure that we will be able to retain the services of any members of our senior management or other key employees. We do not maintain any key person life insurance policies.

Competition for well-qualified employees in all aspects of our business, including software engineers and other technology professionals, is intense both in the U.S. and abroad. Our continued ability to compete effectively depends on our ability to attract new employees and to retain and motivate existing employees. Our software engineers and technology professionals are key to designing code and algorithms necessary to our business. If we do not succeed in attracting well-qualified employees or retaining and motivating existing employees, our business would be adversely affected.

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We process, store and use personal data which exposes us to risks of internal and external security breaches and could give rise to liabilities as a result of governmental regulation and differing personal privacy rights.

We may acquire personal or confidential information from travelers who use our websites and mobile applications. Substantial or ongoing security breaches to our system, whether resulting from internal or external sources, could significantly harm our business. It is possible that advances in computer circumvention capabilities, new discoveries or other developments, including our own acts or omissions, could result in a compromise or breach of personal and confidential traveler information.

We cannot guarantee that our existing security measures will prevent security breaches or attacks. A party, whether internal or external, that is able to circumvent our security systems could steal traveler information or proprietary information or cause significant interruptions in our operations. In the past we have experienced “denial-of-service” type attacks on our system that have made portions of our website unavailable for periods of time. We may need to expend significant resources to protect against security breaches or to address problems caused by breaches, and reductions in website availability could cause a loss of substantial business volume during the occurrence of any such incident. The risk of such security breaches is likely to increase as we expand the number of places where we operate and as the tools and techniques used in these types of attacks become more advanced. Security breaches could result in negative publicity, damage our reputation, expose us to risk of loss or litigation and possible liability and subject us to regulatory penalties and sanctions. Security breaches could also cause travelers and potential users to lose confidence in our security, which would have a negative effect on the value of our brand. Our insurance policies carry low coverage limits and would likely not be adequate to reimburse us for losses caused by security breaches.

Companies that we have acquired, and that we may acquire in the future, may employ security and networking standards at levels we find unsatisfactory. The process of enhancing infrastructure to improve security and network standards may be time consuming and expensive and may require resources and expertise that are difficult to obtain. Acquisitions could also increase the number of potential vulnerabilities and could cause delays in detection of an attack, or the timelines of recovery from an attack. Failure to adequately protect against attacks or intrusions could expose us to security breaches of, among other things, personal user data and credit card information that would have an adverse impact on our business, results of operations and financial condition.

We also face risks associated with security breaches affecting third parties conducting business over the Internet. People generally are concerned with security and privacy on the Internet, and any publicized security problems could inhibit the growth of our business. Additionally, security breaches at third parties upon which we rely, such as travel suppliers, could result in negative publicity, damage our reputation, expose us to risk of loss or litigation and possible liability and subject us to regulatory penalties and sanctions.

We currently provide users with the option to complete certain hotel bookings directly through our websites and mobile applications. We also currently facilitate the purchase of airlines tickets through our mobile applications and assist users in completing transactions directly with travel suppliers. In connection with facilitating these transactions, we receive and store certain personally identifiable information, including credit card information. This information is increasingly subject to legislation and regulations in numerous jurisdictions around the world, including the Commission of the European Union through its Data Protection Directive and variations of that directive in the member states of the European Union. Government regulation is typically intended to protect the privacy of personal information that is collected, processed and transmitted in or from the governing jurisdiction. We could be adversely affected if legislation or regulations are expanded to require changes in our business practices or if governing jurisdictions interpret or implement their legislation or regulations in ways that negatively affect our business, results of operations and financial condition.

Litigation could distract management, increase our expenses or subject us to material money damages and other remedies.

We are involved in various legal proceedings, including, but not limited to, actions relating to breach of contract and intellectual property infringement that involve claims for substantial amounts of money or for other

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relief or that might necessitate changes to our business or operations. Please see the discussion regarding those matters in the section entitled “Business—Legal Proceedings.” Regardless of whether any claims against us are valid, or whether we are ultimately held liable or subject to payment of damages, claims may be expensive to defend and may divert management’s time away from our operations. If any legal proceedings were to result in an unfavorable outcome, it could have a material adverse effect on our business, financial position and results of operations. Any adverse publicity resulting from actual or potential litigation may also materially and adversely affect our reputation, which in turn could adversely affect our results.

Companies in the Internet, technology and media industries are frequently subject to allegations of infringement or other violations of intellectual property rights. We are currently subject to several patent infringement claims and may be subject to future claims relating to intellectual property rights. As we grow our business and expand our operations we may be subject to intellectual property claims by third parties. We plan to vigorously defend our intellectual property rights and our freedom to operate our business; however, regardless of the merits of the claims, intellectual property claims are often time-consuming and extremely expensive to litigate or settle, and are likely to continue to divert managerial attention and resources from our business objectives. Successful infringement claims against us could result in significant monetary liability or prevent us from operating our business, or portions of our business. Resolution of claims may require us to obtain licenses to use intellectual property rights belonging to third parties, which may be expensive to procure, or we may be required to cease using intellectual property altogether. Many of our agreements with travel suppliers, OTAs and other partners require us to indemnify these entities against third-party intellectual property infringement claims, which would increase our defense costs and may require that we pay damages if there were an adverse ruling in any such claims. Any of these events could have a material adverse effect on our business, results of operations or financial condition.

Acquisitions and investments could result in operating difficulties, dilution and other harmful consequences.

We have acquired a number of businesses in the past, including our acquisitions of SideStep, Inc., or SideStep, swoodoo AG, or swoodoo, and JaBo Software Vertrieb-und Entwicklung GmbH, or JaBo Software. We expect to continue to evaluate and enter into discussions regarding a wide array of potential strategic transactions. Any transactions that we enter into could be material to our financial condition and results of operations. The process of integrating an acquired company, business or technology may create unforeseen operating difficulties and expenditures. The areas where we face risks include:

• diversion of management time and focus from operating our business to acquisition integration challenges;

• implementation or remediation of controls, procedures and policies at the acquired company;

• coordination of product, engineering and sales and marketing functions;

• retention of employees from the businesses we acquire;

• liability for activities of the acquired company before the acquisition;

• litigation or other claims in connection with the acquired company; and

• in the case of foreign acquisitions, the need to integrate operations across different cultures and languages and to address the particular economic, currency, political and regulatory risks associated with specific countries.

Our failure to address these risks or other problems encountered in connection with our past or future acquisitions and investments could cause us to fail to realize the anticipated benefits of such acquisitions or investments, incur unanticipated liabilities and harm our business generally.

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The requirements of being a public company may strain our resources and distract our management, which could make it difficult to manage our business, particularly after we are no longer an “emerging growth company”.

Following the completion of this offering, we will be required to comply with various regulatory and reporting requirements, including those required by the Securities and Exchange Commission, or the SEC. Complying with these reporting and other regulatory requirements will be time-consuming and will result in increased costs to us and could have a negative effect on our business, results of operations and financial condition.

As a public company, we will be subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, or the Exchange Act, and requirements of the Sarbanes-Oxley Act of 2002, as amended, or SOX. These requirements may place a strain on our systems and resources. The Exchange Act requires that we file annual, quarterly and current reports with respect to our business and financial condition. The SOX requires that we maintain effective disclosure controls and procedures and internal controls over financial reporting. To maintain and improve the effectiveness of our disclosure controls and procedures, we will need to commit significant resources, hire additional staff and provide additional management oversight. We will be implementing additional procedures and processes for the purpose of addressing the standards and requirements applicable to public companies. Sustaining our growth also will require us to commit additional management, operational and financial resources to identify new professionals to join our firm and to maintain appropriate operational and financial systems to adequately support expansion. These activities may divert management’s attention from other business concerns, which could have a material adverse effect on our business, financial condition, results of operations and cash flows.

As an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 enacted on April 5, 2012, which we refer to as the JOBS Act, we may take advantage of certain temporary exemptions from various reporting requirements including, but not limited to, not being required to comply with the auditor attestation requirements of Section 404 of SOX (and rules and regulations of the SEC thereunder, which we refer to as Section 404) and reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements. In addition, we have elected under the JOBS Act to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are made applicable to private companies.

When these exemptions cease to apply, we expect to incur additional expenses and devote increased management effort toward ensuring compliance with them. We cannot predict or estimate the amount of additional costs we may incur as a result of becoming a public company or the timing of such costs.

Fluctuations in our financial results make quarterly comparisons and financial forecasting difficult, which could make it difficult to manage our business.

Our revenues and operating results have varied significantly from quarter to quarter because our business experiences seasonal fluctuations, which reflect seasonal trends for the travel products distributed through and advertised on our platform. Traditional leisure travel bookings in the U.S. and Europe are generally higher in the second and third calendar quarters of the year as travelers take spring and summer vacations. In the fourth quarter of the calendar year, demand for travel services in the U.S. and Europe generally declines. We have seen and expect to continue to see, that the most significant portion of our revenues will be earned in the second and third quarters. The current state of the global economic environment, combined with the seasonal nature of our business and our relatively limited operating history, makes forecasting future operating results difficult. Because our business is changing and evolving, our historical operating results may not be useful to you in predicting our future operating results. Advertising spending has historically been cyclical in nature, reflecting overall economic conditions as well as individual travel patterns. Our rapid growth has tended to mask the cyclicality and seasonality of our business. As our growth rate slows, the cyclicality and seasonality in our business will become more pronounced and cause our operating results to fluctuate.

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Any significant disruption in service on our websites or in our computer systems, which are currently hosted primarily by third-party providers, could damage our reputation and result in a loss of users, which would harm our business and operating results.

Our brands, reputation and ability to attract and retain travelers to use our websites and mobile applications depend upon the reliable performance of our network infrastructure and content delivery processes. We have experienced interruptions in these systems in the past, including server failures that temporarily slowed down the performance of our websites and mobile applications, and we may experience interruptions in the future. Interruptions in these systems, whether due to system failures, computer viruses or physical or electronic break-ins, could affect the security or availability of our services on our websites and mobile applications and prevent or inhibit the ability of travelers to access our services. Problems with the reliability or security of our systems could harm our reputation, and damage to our reputation and the cost of remedying these problems could negatively affect our business, financial condition and results of operations.

Substantially all of the communications, network and computer hardware used to operate our website are located at facilities in Medford and Somerville, Massachusetts and, with respect to our swoodoo operations, Freiburg, Germany. We do not own or control the operation of these facilities. Our systems and operations are vulnerable to damage or interruption from fire, flood, power loss, telecommunications failure, terrorist attacks, acts of war, electronic and physical break-ins, computer viruses, earthquakes and similar events. The occurrence of any of the foregoing events could result in damage to our systems and hardware or could cause them to fail completely, and our insurance may not cover such events or may be insufficient to compensate us for losses that may occur. Our systems are not completely redundant, so a failure of our system at one site could result in reduced functionality for our travelers, and a total failure of our systems at both U.S. sites could cause our websites or mobile applications to be inaccessible by our travelers. Problems faced by our third-party web hosting providers with the telecommunications network providers with which they contract or with the systems by which they allocate capacity among their customers, including us, could adversely affect the experience of our travelers. Our third-party web hosting providers could decide to close their facilities without adequate notice. Any financial difficulties, such as bankruptcy reorganization, faced by our third-party web hosting providers or any of the service providers with whom they contract may have negative effects on our business, the nature and extent of which are difficult to predict. If our third-party web hosting providers are unable to keep up with our growing needs for capacity, this could have an adverse effect on our business. Any errors, defects, disruptions or other performance problems with our services could harm our reputation and have an adverse effect on our business, financial condition and results of operations.

Governmental regulation and associated legal uncertainties could limit our ability to expand our product offerings or enter into new markets and could require us to expend significant resources, including the attention of senior management, to review and comply with such regulations.

Many of the services we offer are regulated by federal and state governments, and our ability to provide these services is and will continue to be affected by government regulations. The implementation of unfavorable regulations or unfavorable interpretations of existing regulations by courts or regulatory bodies could require us to incur significant compliance costs, cause the development of the affected markets to become impractical and otherwise have a material adverse effect on our business, results of operations and financial condition.

In particular, the Department of Transportation, or DOT, regulates the advertising and sale of air transportation. The DOT actively enforces its regulations and recently made significant changes to the regulations and standards that apply to air carriers and ticket agents. While we are neither an air carrier nor a ticket agent, to the extent we expand our business model in the air transportation area to facilitate bookings, we could become subject to DOT oversight, which would require us to incur significant compliance costs and may require us to change our business practices with respect to the display of airfare and airfare advertising.

In addition, our business strategy involves expansion into regions around the world, many of which have different legislation, regulatory environments, tax laws and levels of political stability. Compliance with foreign

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legal, regulatory or tax requirements will place demands on our time and resources, and we may nonetheless experience unforeseen and potentially adverse legal, regulatory or tax consequences.

We assist with the processing of customer credit card transactions which results in us receiving and storing personally identifiable information. This information is increasingly subject to legislation and regulations in numerous jurisdictions around the world. This legislation and regulation is generally intended to protect the privacy and security of personal information, including credit card information, that is collected, processed and transmitted in or from the governing jurisdiction. We could be adversely affected if government regulations require us to significantly change our business practices with respect to this type of information.

If we are not successful in our ongoing arbitration disputes with Orbitz Worldwide, Inc., we may be required to pay money damages and cease offering certain advertising products.

We are currently a party to two arbitration disputes with Orbitz Worldwide, Inc., or Orbitz. In the first dispute, Orbitz contends that we violated certain exclusivity provisions by our display of certain core query results. We may be ordered to pay Orbitz damages in connection with certain limited displays, and we may be required to stop displaying certain suppliers, which could adversely impact our total revenues.

In the second arbitration, Orbitz contends that we violated our 2009 Promotion Agreement by failing to abide by certain exclusivity provisions relating to the display of certain hotel booking functionality on our websites. If we are not successful in defending against these claims, we may be forced to pay money damages to Orbitz, and we may be required to stop using certain third-party booking and fulfillment providers, which could adversely impact our total revenues.

Fluctuations in foreign currency exchange rates affect financial results in U.S. dollar terms and could negatively impact our financial results.

A portion of our revenues come from international operations. Revenues generated and expenses incurred by our international subsidiaries are often denominated in local currencies. As a result, our consolidated U.S. dollar financial statements are subject to fluctuations due to changes in exchange rates as the financial results of our international subsidiaries are translated from local currencies into U.S. dollars. Our financial results are subject to changes in exchange rates that impact the settlement of transactions in non local currencies.

Risks Related to Our Intellectual Property

We may not be able to adequately protect our intellectual property, which could harm the value of our brands and adversely affect our business.

We regard our intellectual property as critical to our success, and we rely on trademark, copyright and patent law, trade secret protection and confidentiality and/or license agreements to protect our proprietary rights. If we are not successful in protecting our intellectual property, it could have a material adverse effect on our business, results of operations and financial condition.

While we believe that our issued patents and pending patent applications help to protect our business, there can be no assurance that our operations do not, or will not, infringe valid, enforceable third-party patents of third parties or that competitors will not devise new methods of competing with us that are not covered by our patents or patent applications. There can also be no assurance that our patent applications will be approved, that any patents issued will adequately protect our intellectual property, or that such patents will not be challenged by third parties or found to be invalid or unenforceable or that our patents will be effective in preventing third parties from utilizing a copycat business model to offer the same service in one or more categories. Moreover, we rely on intellectual property and technology developed or licensed by third parties, and we may not be able to obtain or continue to obtain licenses and technologies from these third parties at all or on reasonable terms.

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Effective trademark, service mark, copyright and trade secret protection may not be available in every country in which our services are provided. The laws of certain countries do not protect proprietary rights to the same extent as the laws of the U.S. and, therefore, in certain jurisdictions, we may be unable to protect our proprietary technology adequately against unauthorized third party copying or use, which could adversely affect our competitive position. We have licensed in the past, and expect to license in the future, certain of our proprietary rights, such as trademarks or copyrighted material, to third parties. These licensees may take actions that might diminish the value of our proprietary rights or harm our reputation, even if we have agreements prohibiting such activity. Also to the extent third parties are obligated to indemnify us for breaches of our intellectual property rights, these third parties may be unable to meet these obligations. Any of these events could have a material adverse effect on our business, results of operations or financial condition.

Claims by third parties that we infringe their intellectual property rights could result in significant costs and have a material adverse effect on our business, results of operations or financial condition.

We are currently subject to various patent infringement claims. These claims allege, among other things, that our website technology infringes upon owned patent technology. If we are not successful in defending ourselves against these claims, we may be required to pay money damages, which could have an adverse effect on our results of operations. In addition, the costs associated with the loss of these claims could have an adverse effect on our results of operations. Please see the discussion regarding these claims in the section entitled “Business—Legal Proceedings.” We may be subject to future claims relating to our intellectual property rights. As we grow our business and expand our operations we expect that we will continue to be subject to intellectual property claims. Resolving intellectual property claims may require us to obtain licenses to use intellectual property rights belonging to third parties, which may be expensive to procure, or we may be required to cease using intellectual property altogether. Any of these events could have a material adverse effect on our business, results of operations or financial condition.

Confidentiality agreements with employees and others may not adequately prevent disclosure of trade secrets and other proprietary information.

A substantial amount of our processes and technologies is protected by trade secret laws. In order to protect these technologies and processes, we rely in part on confidentiality agreements with our employees, licensees, independent contractors and other advisors. These agreements may not effectively prevent disclosure of confidential information, including trade secrets, and may not provide an adequate remedy in the event of unauthorized disclosure of confidential information. In addition, others may independently discover our trade secrets and proprietary information, and in such cases we could not assert any trade secret rights against such parties. To the extent that our employees, contractors or other third parties with which we do business use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions. Laws regarding trade secret rights in certain markets in which we operate may afford little or no protection to our trade secrets. The loss of trade secret protection could make it easier for third parties to compete with our products by copying functionality. In addition, any changes in, or unexpected interpretations of, the trade secret and other intellectual property laws in any country in which we operate may compromise our ability to enforce our trade secret and intellectual property rights. Costly and time-consuming litigation could be necessary to enforce and determine the scope of our proprietary rights, and failure to obtain or maintain trade secret protection could adversely affect our business, revenue, reputation and competitive position.

Our use of “open source” software could adversely affect our ability to offer our services and subject us to possible litigation.

We use open source software in connection with our development. From time to time, companies that use open source software have faced claims challenging the use of open source software and/or compliance with open source license terms. We could be subject to suits by parties claiming ownership of what we believe to be

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open source software, or claiming noncompliance with open source licensing terms. Some open source licenses require users who distribute software containing open source to make available all or part of such software, which in some circumstances could include valuable proprietary code of the user. While we monitor the use of open source software and try to ensure that none is used in a manner that would require us to disclose our proprietary source code or that would otherwise breach the terms of an open source agreement, such use could inadvertently occur, in part because open source license terms are often ambiguous. Any requirement to disclose our proprietary source code or pay damages for breach of contract could be harmful to our business, results of operations or financial condition, and could help our competitors develop products and services that are similar to or better than ours.

Risks Related to this Offering and Ownership of Our Class A Common Stock

Our securities have no prior market and an active trading market may not develop, which may cause our Class A common stock to trade at a discount from the initial public offering price.

Prior to this offering, there has been no public market for our Class A common stock. The initial public offering price for our Class A common stock will be determined through negotiations between us and the representatives of the underwriters and may not be indicative of the market price of our Class A common stock after this offering. If you purchase shares of our Class A common stock, you may not be able to resell those shares at or above the initial public offering price. We cannot predict the extent to which investor interest in us will lead to the development of an active trading market on The NASDAQ Stock Market or otherwise or how liquid that market might become. An active public market for our Class A common stock may not develop or be sustained after the offering. If an active public market does not develop or is not sustained, it may be difficult for you to sell your shares of Class A common stock at a price that is attractive to you, or at all.

Our stock price may be volatile or may decline regardless of our operating performance, and you may not be able to resell your shares at or above the initial public offering price and the price of our Class A common stock may fluctuate significantly.

After this offering, the market price for our Class A common stock is likely to be volatile, in part because our shares have not been traded publicly. In addition, the market price of our Class A common stock may fluctuate significantly in response to a number of factors, most of which we cannot control, including:

• traveler preferences and competition from other travel sites;

• changes in general economic or market conditions or trends in our industry or the economy as a whole and, in particular, in the leisure travel environment;

• changes in key personnel;

• entry into new geographic markets;

• actions and announcements by us or our competitors or significant acquisitions, divestitures, strategic partnerships, joint ventures or capital commitments;

• changes in operating performance and stock market valuations of other Internet companies;

• investors’ perceptions of our prospects and the prospects of the online travel industry;

• fluctuations in quarterly operating results, as well as differences between our actual financial and operating results and those expected by investors;

• the public’s response to press releases or other public announcements by us or third parties, including our filings with the SEC;

• announcements relating to litigation;

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• guidance, if any, that we provide to the public, any changes in this guidance or our failure to meet this guidance;

• changes in financial estimates or ratings by any securities analysts who follow our Class A common stock, our failure to meet these estimates or failure of those analysts to initiate or maintain coverage of our Class A common stock;

• the development and sustainability of an active trading market for our Class A common stock;

• future sales of our Class A common stock by our officers, directors and significant stockholders; and

• changes in accounting principles.

These and other factors may lower the market price of our Class A common stock, regardless of our actual operating performance. As a result, our Class A common stock may trade at prices significantly below the initial public offering price.

The stock markets, including The NASDAQ Stock Market, have experienced extreme price and volume fluctuations that have affected and continue to affect the market prices of equity securities of many Internet companies. In the past, stockholders have instituted securities class action litigation following periods of market volatility. If we were involved in securities litigation, we could incur substantial costs and our resources and the attention of management could be diverted from our business.

Future sales of our Class A common stock, or the perception in the public markets that these sales may occur, may depress our stock price.

Sales of substantial amounts of our Class A common stock in the public market after this offering, or the perception that these sales could occur, could adversely affect the price of our Class A common stock and could impair our ability to raise capital through the sale of additional shares. Upon completion of this offering, we will have approximately          shares of Class A common stock outstanding, including the shares of Class A common stock issuable pursuant to the automatic adjustment, and approximately          shares of Class B common stock outstanding, and there will be approximately          shares of Class A common stock issuable upon conversion of outstanding shares of Class B common stock. In addition, certain of our existing stockholders have the right to purchase additional shares of Class A common stock based on the initial public offering price as described under “Concurrent Private Placements.” Our shares of Class A common stock offered in this offering will be freely tradable without restriction under the Securities Act, except for any shares of our Class A common stock that may be held or acquired by our directors, executive officers and other affiliates, as that term is defined in the Securities Act, which will be restricted securities under the Securities Act. Restricted securities may not be sold in the public market unless the sale is registered under the Securities Act or an exemption from registration is available.

KAYAK, each of our officers, directors and substantially all of our other existing stockholders have agreed with the underwriters, subject to certain exceptions, not to dispose of or hedge any of the shares of our common stock or securities convertible into or exchangeable for shares of our common stock during the period from the date of this prospectus continuing through the date 180 days after the date of this prospectus, without the prior written consent of Morgan Stanley & Co. LLC, or Morgan Stanley. Collectively, the holders of our securities subject to these restrictions own approximately 33,520,954 shares of our Class B common stock and              shares of our Class A common stock, representing approximately             % of our outstanding common stock assuming conversion into Class B common stock of all capital stock held by those holders upon completion of this offering, and after giving effect to the offering and to the issuance of Class A common stock pursuant to the automatic adjustment. See “Underwriters” for a more detailed description of the terms of these “lock-up” arrangements. All of our shares of Class A common stock outstanding as of the date of this prospectus, and all of our shares of Class A common stock issuable upon conversion of the shares of Class B common stock outstanding as of the completion of this offering, may be sold in the public market by existing

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stockholders 180 days after the date of this prospectus, subject to applicable volume and other limitations imposed under federal securities laws. As a result, assuming that we issue and sell              shares of our Class A common stock in this offering and there are no further issuances of our securities, the holders of our securities subject to these restrictions will be entitled to sell approximately     % of our total common stock 180 days after the date of this prospectus. See “Shares Eligible for Future Sale” for a more detailed description of the restrictions on selling shares of our common stock after this offering. Sales by our existing stockholders of a substantial number of shares in the public market, or the threat of a substantial sale, could cause the market price of our Class A common stock to decrease significantly.

In the future, we may also issue our securities in connection with investments or acquisitions. The amount of shares of our Class A common stock issued in connection with an investment or acquisition could constitute a material portion of our then-outstanding shares of our Class A common stock. Any issuance of additional securities in connection with investments or acquisitions may result in additional dilution to you.

If securities or industry analysts do not publish research or publish inaccurate or unfavorable research about our business, our stock price and trading volume could decline.

The trading market for our Class A common stock will depend in part on the research and reports that securities or industry analysts publish about us or our business. We do not currently have and may never obtain research coverage by securities and industry analysts. If no securities or industry analysts commence coverage of our company, the trading price for our Class A common stock would be negatively impacted. If we obtain securities or industry analyst coverage and if one or more of the analysts who cover us downgrades our Class A common stock or publishes inaccurate or unfavorable research about our business, our stock price would likely decline. If one or more of these analysts cease coverage of us or fail to publish reports on us regularly, demand for our Class A common stock could decrease, which could cause our stock price and trading volume to decline.

Our internal controls over financial reporting may not be effective and our independent registered public accounting firm may not be able to certify as to their effectiveness, which could have a significant and adverse effect on our business and reputation.

We are not currently required to comply with SEC rules that implement Sections 302 and 404 of SOX, and are therefore not required to make a formal assessment of the effectiveness of our internal controls over financial reporting for that purpose. If we opt to rely on the exemptions provided in the JOBS Act, we will be required to comply with these rules upon ceasing to be an “emerging growth company.”

When evaluating our internal controls over financial reporting, we may identify material weaknesses that we may not be able to remediate in time to meet the applicable deadline imposed upon us for compliance with the requirements of Section 404. In addition, if we fail to achieve and maintain the adequacy of our internal controls, as such standards are modified, supplemented or amended from time to time, we may not be able to ensure that we can conclude on an ongoing basis that we have effective internal controls over financial reporting in accordance with Section 404. We cannot be certain as to the timing of completion of our evaluation, testing and any remediation actions or the impact of the same on our operations. If we are not able to implement the requirements of Section 404 in a timely manner or with adequate compliance, our independent registered public accounting firm may issue an adverse opinion due to ineffective internal controls over financial reporting and we may be subject to sanctions or investigation by regulatory authorities, such as the SEC. As a result, there could be a negative reaction in the financial markets due to a loss of confidence in the reliability of our financial statements. In addition, we may be required to incur costs in improving our internal control system and the hiring of additional personnel. Any such action could negatively affect our results of operations and cash flows.

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We are an “emerging growth company” and we cannot be certain if the reduced disclosure requirements applicable to emerging growth companies will make our common stock less attractive to investors.

We are an “emerging growth company,” as defined in the JOBS Act, and we may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not “emerging growth companies” including, but not limited to, not being required to comply with the auditor attestation requirements of Section 404, and reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements. In addition, we have elected under the JOBS Act to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are made applicable to private companies. We cannot predict if investors will find our Class A common stock less attractive if we rely on these exemptions. If some investors find our Class A common stock less attractive as a result, there may be a less active trading market for our Class A common stock and our stock price may be more volatile.

Our management and other affiliates have significant control of our common stock and could control our actions in a manner that conflicts with the interests of other stockholders.

After giving effect to the offering, our Class B common stock will have ten votes per share and our Class A common stock, which is the stock we are selling in this offering, will have one vote per share. We anticipate that our executive officers, directors and their affiliated entities together will beneficially own approximately           % of our Class B common stock, representing approximately           % of the voting power of our outstanding capital stock, assuming the exercise of options, warrants and other common stock equivalents which are currently exercisable and held by these stockholders. In addition, because of this dual class structure, our executive officers, directors and their affiliated entities will continue to be able to control all matters submitted to our stockholders for approval even if they come to own less than 50% of the outstanding shares of our common stock. As a result, these stockholders, acting together, will be able to exercise considerable influence over matters requiring approval by our stockholders, including the election of directors, and may not always act in the best interests of other stockholders. Such a concentration of ownership may have the effect of delaying or preventing a change in our control, including transactions in which our stockholders might otherwise receive a premium for their shares over then current market prices.

We do not expect to pay any cash dividends for the foreseeable future.

The continued operation and growth of our business will require substantial cash. Accordingly, we do not anticipate that we will pay any cash dividends on shares of our Class A common stock for the foreseeable future. Any determination to pay dividends in the future will be at the discretion of our board of directors and will depend upon our results of operations, financial condition, contractual restrictions relating to indebtedness we may incur, restrictions imposed by applicable law and other factors our board of directors deems relevant. Accordingly, if you purchase shares in this offering, realization of a gain on your investment will depend on the appreciation of the price of our Class A common stock, which may never occur. Investors seeking cash dividends in the foreseeable future should not purchase our Class A common stock.

Antitakeover provisions in our charter documents and Delaware law might discourage or delay acquisition attempts for us that you might consider favorable.

Our amended and restated certificate of incorporation and amended and restated by-laws to be in effect upon completion of this offering will contain provisions that may make the acquisition of us more difficult without the approval of our board of directors. These provisions, among other things:

• authorize the issuance of undesignated preferred stock, the terms of which may be established and the shares of which may be issued without stockholder approval, and which may include supermajority voting, special approval, dividend or other rights or preferences superior to the rights of the holders of common stock;

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• prohibit stockholder action by written consent, which requires all stockholder actions to be taken at a meeting of our stockholders;

• provide that our board of directors is expressly authorized to make, alter or repeal our amended and restated by-laws; and

• establish advance notice requirements for nominations for elections to our board of directors or for proposing matters that can be acted upon by stockholders at stockholder meetings.

These antitakeover provisions and other provisions under Delaware law may prevent new investors from influencing significant corporate decisions, could discourage, delay or prevent a transaction involving a change-in-control, even if doing so would benefit our stockholders. These provisions could also discourage proxy contests and make it more difficult for you and other stockholders to elect directors of your choosing and to cause us to take other corporate actions you desire.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, including the sections entitled “Prospectus Summary,” “Risk Factors,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and “Business,” contains forward-looking statements concerning our business, operations and financial performance and condition as well as our plans, objectives and expectations for our business operations and financial performance and condition. Any statements that are not of historical facts may be deemed to be forward-looking statements. You can identify these statements by words such as “aim,” “anticipate,” “assume,” “believe,” “could,” “due,” “estimate,” “expect,” “goal,” “intend,” “may,” “objective,” “plan,” “potential,” “positioned,” “predict,” “should,” “target,” “will,” “would” and other similar expressions or words that convey uncertainty of future events or outcomes to identify these forward-looking statements. These statements are not guarantees of future performance or development and involve known and unknown risks, uncertainties and other factors that are in some cases beyond our control. All of our forward-looking statements are subject to risks and uncertainties that may cause our actual results to differ materially from our expectations. Factors that may cause such differences include, but are not limited to, the risks described under “Risk Factors,” including:

• our ability to maintain or establish relationships with travel suppliers and OTAs;

• our ability to remain competitive by continuing to innovate and provide tools and services that are useful to travelers;

• competition from other travel companies;

• our dependence on a single third party to provide our airfare query results;

• impact on us of changes in general search engine algorithms of major search engines, such as Google, or termination of our advertising arrangements with other travel-related websites;

• our ability to expand our business model beyond providing travelers with travel search results;

• limitations on our ability to expand into and operate in international markets;

• sensitivity of the leisure travel industry to general economic downturns and recessions, natural disasters and other natural phenomena;

• our dependence upon key executive management or our ability to hire or retain additional personnel;

• impact of litigation in which we currently are, or in the future may be, a party;

• failure of our security measures to prevent internal or external security breaches of personal data processed, stored or used by us;

• any significant disruption in service on our website or in our computer systems, which are currently hosted primarily by third-party providers;

• governmental regulation and associated legal uncertainties;

• our ability to adequately protect our intellectual property rights;

• failure of our confidentiality agreements to effectively prevent disclosure of confidential information, including trade secrets, and to provide an adequate remedy in the event of unauthorized disclosure of confidential information; and

• increased strains on our resources of being a public company.

We derive many of our forward-looking statements from our own operating budgets and forecasts, which are based upon many detailed assumptions. While we believe that our assumptions are reasonable, we caution that it is very difficult to predict the impact of known factors, and it is impossible for us to anticipate all factors that could affect our actual results. Important factors that could cause actual results to differ materially from our expectations, or cautionary statements, are disclosed under “Risk Factors” and “Management’s Discussion and

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Analysis of Financial Condition and Results of Operations” in this prospectus. All written and oral forward-looking statements attributable to us, or persons acting on our behalf, are expressly qualified in their entirety by the cautionary statements contained in this prospectus as well as other cautionary statements that are made from time to time in our other SEC filings and public communications. You should evaluate all forward-looking statements made in this prospectus in the context of these risks and uncertainties.

This prospectus also contains estimates and other statistical data made by independent parties and by us relating to market size and growth and other data about our industry. We obtained the industry and market data in this prospectus from our own research as well as from industry and general publications, surveys and studies conducted by third parties, some of which may not be publicly available. This data involves a number of assumptions and limitations and contains projections and estimates of the future performance of the industries in which we operate that are subject to a high degree of uncertainty. We caution you not to give undue weight to such projections, assumptions and estimates. While we believe that these publications, studies and surveys are reliable, we have not independently verified the data contained in them.

Potential investors and other readers are urged to consider these factors carefully in evaluating the forward-looking statements and are cautioned not to place undue reliance on the forward-looking statements. These forward-looking statements speak only as of the date of this prospectus. Unless required by law, we do not intend to update or revise any forward-looking statements publicly to reflect new information or future events or otherwise. You should, however, review the factors and risks we describe in the reports we will file from time to time with the SEC after the date of this prospectus. See “Where You Can Find Additional Information.”

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USE OF PROCEEDS

We estimate that the net proceeds we receive from this offering will be approximately $            million based on the assumed initial public offering price of $            per share, which is the midpoint of the range included on the cover page of this prospectus, after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us. If the underwriters’ option to purchase additional shares in this offering from us is exercised in full, our estimated net proceeds will be approximately $            million, after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us. A $1.00 increase or decrease in the assumed initial public offering price of $            per share would increase or decrease the net proceeds we receive from this offering by approximately $            million, assuming the number of shares offered by us as set forth on the cover page of this prospectus remains the same and after deducting the estimated underwriter discounts and commissions and estimated offering expenses payable by us.

While we do not have any current specific plans for the net proceeds resulting from this offering, we expect to use the net proceeds for working capital and other general corporate purposes. We may also use a portion of the proceeds to expand our current business through acquisitions or investments in other strategic businesses, products or technologies. We have no commitments with respect to any such acquisitions or investments at this time. We will have broad discretion in the way we use the net proceeds, which will afford us significant flexibility to pursue our business strategies.

The primary purposes of this offering are to raise additional working capital, create a public market for our Class A common stock for the benefit of our current stockholders, allow us easier and quicker access to the public markets should we need more capital in the future, increase the profile and prestige of our company with existing and possible future travelers, vendors and strategic partners and make our stock more valuable and attractive to our employees and potential employees for compensation purposes.

We intend to invest the net proceeds in short- and intermediate-term interest-bearing obligations, investment-grade instruments, certificates of deposit or guaranteed obligations of the U.S. government, pending their use as described above.

DIVIDEND POLICY

We have never declared or paid any cash dividends on our capital stock. We do not expect to pay dividends on our capital stock for the foreseeable future. Instead, we anticipate that all of our earnings in the foreseeable future will be retained and used in the operation and growth of our business. Any future determination to pay dividends will be at the discretion of our board of directors, subject to compliance with applicable law and any contractual provisions, including under agreements for indebtedness that we may incur, that may restrict or limit our ability to pay dividends, and will depend upon, among other factors, our results of operations, financial condition, capital requirements and other factors that our board of directors deems relevant.

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CAPITALIZATION

The following table sets forth our cash and cash equivalents and capitalization at December 31, 2011:

• on an actual basis;

• on a pro forma basis to give effect to the conversion of all outstanding shares of our common stock and our redeemable convertible preferred stock into 33,793,123 shares of our Class B common stock; and

• on a pro forma as adjusted basis to reflect: (i) the pro forma basis conversions set forth above, (ii) the sale by us of                  shares of Class A common stock in this offering and our receipt of the estimated net proceeds from that sale, based on an assumed public offering price of $             per share, which is the midpoint of the range set forth on the cover page of this prospectus, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us (iii) the issuance by us of             shares of Class A common stock based on the midpoint of the initial public offering price range set forth on the cover page of this prospectus, for no additional consideration, pursuant to the automatic adjustment described under “Concurrent Private Placements,” and (iv) the filing of our restated certificate of incorporation which will occur prior to the closing of this offering.

Our capitalization following the completion of this offering will be adjusted based on the actual initial public offering price and other terms of this offering determined at pricing. You should read this table together with our consolidated financial statements and the related notes appearing elsewhere in this prospectus and the sections of this prospectus titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Use of Proceeds” and “Selected Consolidated Financial and Operating Data.”

	Actual		Pro Forma		Pro Forma as Adjusted
	(unaudited)
	(in thousands, except share and per share amounts)
Cash and cash equivalents	$	35,127	$	35,127
Redeemable Convertible Preferred Stock(1):
Series A redeemable convertible preferred stock, $0.001 par value: 6,600,000 shares authorized, issued and outstanding	$	9,702	$	—
Series A-1 redeemable convertible preferred stock, $0.001 par value: 1,176,051 shares authorized, issued and outstanding		2,355		—
Series B redeemable convertible preferred stock, $0.001 par value: 4,989,308 shares authorized, issued and outstanding		9,888		—
Series B-1 redeemable convertible preferred stock, $0.001 par value: 2,138,275 shares authorized, issued and outstanding		4,026		—
Series C redeemable convertible preferred stock, $0.001 par value: 3,897,084 shares authorized, 3,855,180 shares issued and outstanding		15,372		—
Series D redeemable convertible preferred stock, $0.001 par value: 8,075,666 shares authorized, 8,008,842 shares issued and outstanding		206,151		—
Total redeemable convertible preferred stock	$	247,494	$	—

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	Actual			Pro Forma			Pro Forma as Adjusted
	(unaudited)
	(in thousands, except share and per share amounts)
Stockholders’ Equity:
Common Stock, $0.001 par value: 45,000,000 shares authorized, 7,025,467 shares issued and outstanding, actual; no shares authorized, issued and outstanding, on a pro forma and pro forma as adjusted basis	$	7		$	—
Class A common stock, $0.001 par value: no shares authorized, issued and outstanding, actual;              shares authorized, issued and outstanding, on a pro forma and pro forma as adjusted basis		—			—
Class B common stock, $0.001 par value: no shares authorized, issued and outstanding, actual; 45,000,000 shares authorized, 33,793,123 issued and outstanding, on a pro forma and pro forma as adjusted basis		—			34
Additional paid-in capital		3,296			250,763
Accumulated other comprehensive income		(977	)		(977	)
Accumulated deficit		(4,050	)		(4,050	)
Total stockholders’ (deficit) equity		(1,724	)		245,770
Total capitalization		245,770			245,770

(1) All redeemable convertible preferred stock assumes no shares authorized, no shares issued and no shares outstanding, on a pro forma and pro forma as adjusted basis.

In the table above, the number of shares outstanding as of December 31, 2011 does not include:

• 103,904 shares of Class B common stock issuable upon the exercise of outstanding warrants at a weighted average exercise price of $13.57 per share;

• 9,086,586 shares of Class B common stock issuable upon the exercise of options outstanding with a weighted average exercise price of $10.79 per share;

• 159,946 shares of Class B common stock reserved for issuance pursuant to future grants of awards under our Third Amended and Restated 2005 Equity Incentive Plan;

•                                   shares of common stock reserved for future grants of awards under the 2012 Equity Incentive Plan as of the date of this prospectus; and

•                                   shares of Class A common stock pursuant to the private placement purchase rights described under “Concurrent Private Placements,” based on an assumed initial public offering price of $             per share, which is the midpoint of the range set forth on the cover of the prospectus.

Each $1.00 increase or decrease in the assumed initial public offering price of $            per share, the midpoint of the range set forth on the cover page of this prospectus, would increase or decrease the amount of cash and cash equivalents by approximately $            million and total stockholders’ equity by approximately $            million, assuming the number of shares offered by us as set forth on the cover page of this prospectus remains the same and after deducting the estimated underwriting discounts and commissions and estimated expenses payable by us and assuming no shares are issued pursuant to the private placement purchase rights described under “Concurrent Private Placements.”

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DILUTION

Dilution is the amount by which the portion of the offering price paid by the purchasers of our Class A common stock in this offering exceeds the net tangible book value per share of our Class A common stock after the offering. Unless otherwise stated, the following descriptions in this section do not include the impact of dilution from the potential issuance of shares of Class A common stock pursuant to the concurrent private placements and assumes no exercise of stock options or conversion of warrants outstanding as of December 31, 2011.

If you invest in our Class A common stock, you will be diluted to the extent the initial public offering price per share of our Class A common stock exceeds the net tangible book value per share of our Class A common stock and Class B common stock immediately after this offering. Our net tangible book value as of December 31, 2011 was approximately $72.4 million, or $10.31 per share of common stock. The net tangible book value per share represents the amount of our tangible net worth, or total tangible assets less total liabilities, divided by 7,025,467 shares of our common stock issued and outstanding as of that date.

The pro forma net tangible book value of our Class A common stock and Class B common stock as of December 31, 2011 was approximately $72.4 million, or $2.14 per share. Pro forma net tangible book value per share represents our total pro forma tangible assets less total pro forma liabilities, divided by 33,793,123 shares, the pro forma number of shares of Class A common stock and Class B common stock outstanding as of December 31, 2011, in each case after giving effect to the conversion of all outstanding convertible preferred stock into Class B common stock.

After giving effect to the issuance and sale of             shares of our Class A common stock to be sold by us in this offering and our receipt of the estimated net proceeds from such sale, based on an assumed public offering price of $            per share, which is the midpoint of the range set forth on the cover page of this prospectus, and after deducting the estimated underwriting discounts and commissions and the estimated expenses of the offering, our pro forma as adjusted net tangible book value per share as of December 31, 2011 would have been approximately $            million, or $            per share. This amount represents an immediate increase in pro forma as adjusted net tangible book value of $            per share to existing stockholders and immediate dilution in pro forma as adjusted net tangible book value of $            per share to new investors purchasing shares of our common stock in this offering.

The following table illustrates the per share dilution to new investors purchasing shares of our common stock in this offering, without giving effect to the over-allotment option granted to the underwriters:

Assumed initial public offering price per share				$
Net tangible book value per share at December 31, 2011, before giving effect to this offering	$	10.31
Decrease per share attributable to conversion of convertible preferred stock and warrants	$	(8.17	)
Pro forma net tangible book value before this offering	$	2.14
Increase in pro forma net tangible book value per share attributable to new investors purchasing shares in this offering		$
Pro forma as adjusted net tangible book value per share after giving effect to this offering					$
Dilution per share to new investors					$

A $1.00 increase (decrease) in the assumed initial public offering price of $            per share would increase (decrease) our pro forma as adjusted net tangible book value by $            million, the pro forma as adjusted net tangible book value per share after this offering by $            and the dilution per share to new investors by $             assuming the number of shares offered by us, as set forth on the cover page of this prospectus, remains

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the same, and after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us.

These amounts may be further increased or decreased due to the concurrent private placements. For example, pursuant to the private placement purchase rights, we may issue up to $9.2 million of Class A common stock at the initial public offering price, if the initial public offering price is less than $31.09 per share. Furthermore, pursuant to the automatic adjustment, if the initial public offering price is less than $27.00 per share we will issue to certain of our existing stockholders a total number of additional shares calculated by taking the amount by which $27.00 exceeds the initial public offering price per share, dividing that excess amount by the initial public offering price per share and, finally multiplying the result by             , which is the number of shares of Series D preferred stock held by the stockholders entitled to the automatic adjustment. Based on an assumed initial public offering price of $             per share, which is the midpoint of the range set forth on the cover of the prospectus, we would issue to such stockholders, for no additional consideration,              additional shares of our Class A common stock. See “Concurrent Private Placements.”

The following table summarizes as of December 31, 2011, after giving effect to this offering and the issuance of shares of Class A common stock, for no additional consideration, pursuant to the automatic adjustment:

• the total number of shares of Class A common stock issued by us, including              shares of Class A common stock issuable pursuant to the automatic adjustment, based on an assumed initial public offering price of $             per share;

• the total consideration paid to us before deducting estimated underwriting discounts and commissions payable by us of $            million and estimated offering expenses of approximately $            million; and

• the average price per share paid by existing stockholders and by new investors who purchase shares of Class A common stock in this offering at the assumed initial public offering price of $             per share.

	Shares Purchased				Total Consideration				Average Price Per Share
	Number	Percent			Amount	Percent
Existing stockholders					$				$
New investors
Total			100	%			100	%

The foregoing table does not reflect options outstanding under our stock option plans or stock options to be granted after the offering or the issuance of shares pursuant to the private placement purchase rights described above and under “Concurrent Private Placements.” Following the offering, there will be 9,086,586 options outstanding with an average exercise price of $10.79 per share and 103,904 warrants outstanding with an average exercise price of $13.57 per share.

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SELECTED CONSOLIDATED FINANCIAL AND OPERATING DATA

The tables on the following pages set forth the consolidated financial and operating data as of and for the periods indicated. The consolidated statements of operations data presented below for the years ended December 31, 2007 and 2008 and the consolidated balance sheet data as of December 31, 2007, 2008, and 2009 have been derived from consolidated financial statements not included in this prospectus. You should read the consolidated financial data presented on the following pages in conjunction with our consolidated financial statements, the notes to our consolidated financial statements and “Management’s Discussion and Analysis of Financial Condition and Results of Operations.

Consolidated Statements of Operations Data:

(in thousands, except share and per share amounts)

	Years ended December 31,
	2007			2008			2009			2010			2011
Revenues	$	48,444		$	112,018		$	112,698		$	170,698		$	224,534
Cost of revenues (excludes depreciation and amortization)		7,497			17,985			15,362			15,630			18,598
Selling, general and administrative expenses:
Marketing		33,624			56,841			57,389			91,721			111,018
Personnel		8,131			19,150			22,638			29,764			40,785
Other general and administrative expenses		2,346			5,743			6,568			9,967			16,400
Total selling, general and administrative expenses (excludes depreciation and amortization)		44,101			81,734			86,595			131,452			168,203
Depreciation and amortization		1,485			5,214			5,380			6,821			8,486
Impairment of intangible assets(1)		—			—			—			—			14,980
Income (loss) from operations		(4,639	)		7,085			5,361			16,795			14,267
Other income (expense)		271			(1,569	)		(1,225	)		3,357			2,115
Income tax expense (benefit)		—			415			(2,776	)		12,120			6,681
Net income (loss)	$	(4,368	)	$	5,101		$	6,912		$	8,032		$	9,701
Net loss per common share (after redeemable convertible preferred stock dividends):
Basic	$	(1.67	)	$	(1.37	)	$	(0.92	)	$	(0.57	)	$	(0.28	)
Diluted	$	(1.67	)	$	(1.37	)	$	(0.92	)	$	(0.57	)	$	(0.28	)
Weighted average shares outstanding:
Basic		3,860,114			4,831,777			5,223,187			6,463,639			7,309,202
Diluted		3,860,114			4,831,777			5,223,187			6,463,639			7,309,202
Unaudited pro forma:(2)
Net income per common share:
Basic													$	0.28
Diluted													$	0.26
Weighted average common shares:
Basic														34,076,858
Diluted														37,740,386
Other Data:
Adjusted EBITDA(3)	$	(1,415	)	$	18,699		$	16,188		$	32,119		$	50,160
Capital expenditures	$	1,043		$	1,092		$	2,269		$	2,273		$	4,260
Queries(4)		238,449			434,540			458,594			634,319			898,573

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Consolidated Balance Sheet Data:

(in thousands)

	December 31,
	2007			2008			2009			2010			2011
Cash and cash equivalents	$	25,061		$	23,609		$	15,950		$	34,966		$	35,127
Working capital		27,984			38,453			36,019			58,629			65,560
Total assets		221,494			232,544			222,823			269,907			277,948
Long-term obligations(5) and redeemable convertible preferred stock		230,330			237,218			225,085			238,246			248,644
Total stockholders’ (deficit)		(23,609	)		(22,940	)		(21,780	)		(450	)		(1,724	)

(1) In January 2011, we determined that we would not support two brand names and URLs in the United States and decided that we would migrate all traffic from sidestep.com to KAYAK.com. As a result, our SideStep brand name and URL intangible assets were impaired and we incurred a related write-down of $15.0 million in the first three months of 2011.

(2) Pro forma information gives effect to the conversion of all outstanding shares of our common stock and our redeemable convertible preferred stock into 33,793,123 shares of our Class B common stock.

(3) Earnings Before Interest, Taxes, Depreciation and Amortization, or EBITDA, is a metric used by management to measure operating performance. Adjusted EBITDA represents EBITDA excluding the impact of stock-based compensation expense and other income (expense), net. We present Adjusted EBITDA as a supplemental performance measure because we believe it facilitates operating performance comparisons from period to period and company to company by backing out potential differences caused by variations in capital structures (affecting other income (expense), net), tax positions (such as the impact on periods or companies of changes in effective tax rates), the age and book depreciation of fixed assets (affecting relative depreciation expense), the impact of acquisitions and the impact of stock-based compensation expense. Because Adjusted EBITDA facilitates internal comparisons of operating performance on a more consistent basis, we also use Adjusted EBITDA in measuring our performance relative to that of our competitors. Adjusted EBITDA is not a measurement of our financial performance under GAAP and should not be considered as an alternative to net income, operating income or any other performance measures derived in accordance with GAAP or as an alternative to cash flow from operating activities as a measure of our profitability or liquidity. We understand that although Adjusted EBITDA is frequently used by securities analysts, lenders and others in their evaluation of companies, Adjusted EBITDA has limitations as an analytical tool, and you should not consider it in isolation, or as a substitute for analysis of our results as reported under GAAP. Some of these limitations are:

• Adjusted EBITDA does not reflect our cash expenditures or future requirements for capital expenditures or contractual commitments;

• Adjusted EBITDA does not reflect changes in, or cash requirements for, our working capital needs;

• although depreciation is a non-cash charge, the assets being depreciated will often have to be replaced in the future, and Adjusted EBITDA does not reflect any cash requirements for such replacements; and

• other companies in our industry may calculate Adjusted EBITDA differently than we do, limiting its usefulness as a comparative measure.

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The following table reconciles income (loss) from operations to EBITDA and Adjusted EBITDA for the periods presented and is unaudited:

	Years ended December 31,
	2007			2008			2009			2010			2011
Income (loss) from operations	$	(4,639	)	$	7,085		$	5,361		$	16,795		$	14,267
Other income (expense), net		62			594			(1,346	)		3,250			2,004
Depreciation and amortization		1,485			5,214			5,380			6,821			8,486
Impairment of intangible assets(1)		—			—			—			—			14,980
EBITDA		(3,092	)		12,893			9,395			26,866			39,737
Stock-based compensation		1,739			6,400			5,447			8,503			12,427
Other (income) expense, net		(62	)		(594	)		1,346			(3,250	)		(2,004	)
Adjusted EBITDA	$	(1,415	)	$	18,699		$	16,188		$	32,119		$	50,160

(4) Queries refer to user requests for travel information we process through our websites and mobile applications.

(5) Long-term obligations includes current and long-term portions of debt, warrant liability and acquisition-related put liability.

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MANAGEMENT’S DISCUSSION AND ANALYSIS OF

FINANCIAL CONDITION AND RESULTS OF OPERATIONS

You should read the following discussion together with our consolidated financial statements and the related notes included elsewhere in this prospectus. This discussion contains forward-looking statements about our business and operations. Our actual results may differ materially from those we currently anticipate as a result of many factors, including those we describe under “Risk Factors” and elsewhere in this prospectus. See “Special Note Regarding Forward-Looking Statements.”

Overview

We are a technology-driven company committed to improving online travel. Cofounders of Expedia, Travelocity and Orbitz started KAYAK in 2004 to take a better approach to online travel. Our websites and mobile applications enable people to easily research and compare accurate and relevant information, including pricing and availability, in one comprehensive, fast and intuitive display. Our software gathers information from multiple sources, including third party providers, travel suppliers and OTAs, and allows users to compare travel information from hundreds of websites. We request information from our data sources based on a user’s travel criteria, and display query results with the broadest set of websites that are relevant to such travel criteria. Once users find their desired flight, hotel or other travel product, KAYAK sends them to their preferred travel supplier or OTA website to complete their purchase, and in many cases, users may now complete hotel bookings directly through our websites and mobile applications. We also provide travel management tools and services such as flight status updates, pricing alerts and itinerary management.

How We Generate Revenues

KAYAK’s services are free for travelers. We earn distribution revenues by sending referrals to travel suppliers and OTAs and by facilitating bookings through our websites and mobile applications, and we earn advertising revenues from advertising placements on our websites and mobile applications. On the distribution side, travel suppliers and OTAs either pay us at the time of referral on a set cost per click, or CPC, basis or after a user completes a transaction on a supplier or OTA website or through the KAYAK booking feature on a fixed cost per acquisition, or CPA, basis or as a percentage of the transaction value.

Advertising revenues primarily come from payments for text-based sponsored links, graphical display advertisements and compare units. A “compare unit” is an advertising placement that, if selected by a KAYAK user, launches the advertiser’s website and initiates a query based on the same travel parameters provided on the KAYAK website. The major types of advertisers on our websites consist of OTAs, third party sponsored link providers, hotels, airlines and vacation package providers. Generally, our advertisers pay us on a CPC basis, which means advertisers pay us only when someone clicks on one of their advertisements, or on a cost per thousand impression basis, or CPM. Paying on a CPM basis means that advertisers pay us based on the number of times their advertisements appear on our websites. We believe that offering advertisers the ability to pay on a CPC or CPM basis provides advertisers the ability to choose the method of payment that best suits their needs and ultimately results in more advertisers choosing to advertise with us.

We generate a significant portion of our revenues from a few large customers. Expedia and its affiliated brands, including Hotels.com and Hotwire, together accounted for 23.9% of our total revenues for the year ended December 31, 2011. We have separate contracts with respect to Expedia and each of its affiliated brands, each of which have varying terms and expiration dates. Orbitz accounted for 12.3% of total revenues for the year ended December 31, 2011. Our contract with Orbitz expires on December 31, 2013.

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Highlights and Trends

Revenue Growth

Our revenue for the year ended December 31, 2011 was $224.5 million, a 31.5% increase over the year ended December 31, 2010. This increase in revenue is primarily due to increased travel queries on our websites and mobile applications, which increased 41.7% in 2011, over the comparable period in 2010. We believe that traffic and queries on our websites and mobile applications will continue to increase as more people learn about our websites and our brand.

Brand Marketing

We began investing in brand advertising, including TV advertisements and billboards, in late 2009. For the year ended December 31, 2011 and for the year ended December 31, 2010, we spent $57.7 million and $43.7 million on these activities, respectively. We believe that this investment contributed significantly to our revenue growth. Brand awareness is an important part of our growth strategy and we expect to continue to invest at this level or above in brand marketing for the foreseeable future.

Hotel Growth

We intend to expand our hotel offerings. For the year ended December 31, 2011, hotel revenue increased by $9.8 million or 40.0% as compared to the year ended December 31, 2010. We believe that the number of consumer choices, combined with the predominantly fixed nature of hotel operating costs, results in a willingness of hoteliers to pay a premium for quality referrals and offers attractive opportunities for future growth.

International Expansion

Our revenues from international operations accounted for approximately 18% of our total revenue for the year ended December 31, 2011. We acquired swoodoo in May 2010 and checkfelix.com in April 2011. As a result of these acquisitions, and organic growth of the KAYAK brand, our international revenues grew to approximately $40.1 million during 2011 from approximately $16.0 million during 2010. We believe that these strategic acquisitions, along with the establishment of our European headquarters in Zurich, Switzerland, have strengthened our presence and team in Europe, and we plan to continue to invest in our international team and brands. We expect our revenues from international operations to increase at a rate faster than revenues from our U.S. operations.

Mobile Products

We offer several mobile applications that allow people to use our services from smart phones such as the iPhone, Blackberry and phones running on the Android operating system and tablet devices such as the iPad. These applications extend the availability of our services beyond traditional computers and allow users greater access to KAYAK’s services. Queries conducted on our mobile applications accounted for 14.1% of our total queries for the year ended December 31, 2011. However, we estimate mobile applications accounted for approximately 2% of total revenues during the year. We believe mobile applications will continue to gain popularity, and we expect to continue to commit resources to improve the features, functionality and commercialization of our mobile applications. We also believe that over time mobile applications will begin to contribute meaningful revenue to our business.

Cash and Debt

We had cash and cash equivalents and marketable securities of $46.3 million as of December 31, 2011 and no outstanding long- or short-term debt. Given the recent financial turmoil and low interest rates, we hold most of our funds as cash and cash equivalents or marketable securities, and the rest is invested in highly rated money market funds and commercial paper.

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Results of Operations

Our results of operations as a percentage of revenue and period-over-period variances are discussed below. All dollars and query amounts are presented in thousands.

Operating Metrics

Our operating results are affected by certain key metrics. These metrics help us to predict financial results and evaluate our business. These metrics consist of queries and revenue per thousand queries.

Queries and Revenue per Thousand Queries

Queries refer to user queries for travel information we process through our websites and mobile applications. We count a separate query each time a user requests travel information through one of our websites or mobile applications. Therefore, a user visit to one of our websites may result in no queries being counted, or in multiple queries being counted, depending on the activity of the user during that visit. On average, approximately 1.1 queries have historically been conducted during a typical user visit to our websites.

We use revenue per thousand queries, or RPM, to measure how effectively we convert user queries to revenues. RPM is calculated as total revenues divided by total thousand queries.

We use query metrics to understand historical revenue performance, and to help in forecasting future revenues. In particular, RPM is a key operating statistic that we use in our analysis of past performance and in connection with our evaluation of potential changes to our business model and operating activities.

Revenues

	Year ended December 31,						%  increase (decrease) 2009 to 2010			% increase 2010 to 2011
	(Amounts in thousands (except RPM))
	2009		2010		2011
Revenues	$	112,698	$	170,698	$	224,534		51.5	%		31.5	%
Queries		458,594		634,319		898,573		38.3	%		41.7	%
RPM	$	246	$	269	$	250		9.3	%		(7.1	)%

Revenues for the year ended December 31, 2011 increased $53.8 million over the same period in 2010 primarily due to a 41.7% increase in query volume. We attribute the increase in query volume to a variety of factors including our investment in marketing activities, the acquisition of swoodoo in May 2010 and checkfelix.com in April 2011, and our partnership with Bing Travel which began in March 2011. The increase in query volume was partially offset by a reduction in RPM due to an increase in mobile queries, for which we earn revenue at a lower rate. Mobile queries were 14.1% of total queries in 2011, as compared to 8.2% in 2010.

Revenues for the year ended December 31, 2010 increased over the same period in 2009 primarily due to a 38.3% increase in website queries. These additional queries accounted for $43.2 million of the $58.0 million increase. During the same period average revenue per thousand queries increased 9.3%, primarily as a result of improved advertising sales. Our acquisition of swoodoo contributed $8.0 million to our revenues in 2010.

Cost of revenues (excludes depreciation and amortization)

Cost of revenues consists of fees we pay to third parties to process airfare queries and expenses associated with operating and maintaining our data centers. Additionally in 2009, these costs included advertising syndication expenses. Our syndication activities consisted of placing text-based advertisements on other websites

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in exchange for a portion of the total revenues that we receive from those advertisements. We included the portion of revenues remitted to our syndication partners in cost of revenues. We cancelled the majority of our advertising syndication contracts in April 2009 to focus on our core business, resulting in decreased cost as a percentage of revenues from 2009 to 2010.

	Year ended December 31,
	(Dollar amounts in thousands)						% increase 2009 to 2010		% increase 2010 to 2011
	2009		2010		2011
Cost of revenues	$	15,362	$	15,630	$	18,598		1.7%		19.0%
% of total revenues		13.6%		9.2%		8.3%

Our cost of revenues increased $3.0 million in 2011 as compared to 2010, due to higher data center costs and air query fees. Data center costs increased $1.6 million for the year ended December 31, 2011 as compared to the same period in 2010 due to expenses incurred to process and improve overall query speed and efficiency. Additionally, our air query fees increased $1.3 million in 2011 compared to 2010 due to increased query volume, partially offset by a lower cost per query. Our air query fees have a tiered pricing structure whereby increased volume results in a lower overall cost per query.

Our cost of revenues were relatively flat for the year ended December 31, 2010 compared to the same period in 2009 due primarily to higher volume-driven air query fees of $1.6 million and data center costs of $0.7 million, partially offset by the elimination of advertising syndication costs of $2.2 million discussed above.

Selling, general and administrative expenses (excludes depreciation and amortization)

Selling, general and administrative expenses consist of marketing, technology, personnel and other costs, which are more fully described below.

Marketing

Marketing consists of online marketing, brand marketing and other marketing expenses. Online marketing includes search engine fees and contextual advertising placements. Search engine fees are fees we pay to Google and Yahoo for our advertisements to appear on their result pages when users search certain travel-related keywords on the search engine’s website. We pay contextual advertisement fees to advertise on other travel-related websites. These advertisements generally consist of the placement of a KAYAK logo or a check-box next to the KAYAK name and often allow users who click on our contextual advertisements to launch a query on KAYAK using previously entered search parameters. Brand marketing expense includes TV, billboards and display advertisements, and creative development fees. Other marketing includes affiliate marketing, public relations, and other general marketing costs. Affiliate marketing refers to revenue sharing fees we pay to other travel-related websites that drive traffic to KAYAK through use of their own marketing resources. Under our affiliate marketing program, we provide our services through third party websites and pay them a percentage of any revenues received from these services.

	Year ended December 31,
	(Dollar amounts in thousands)						% increase 2009 to 2010		% increase 2010 to 2011
	2009		2010		2011
Brand marketing	$	15,418	$	43,702	$	57,715		183.4%		32.1%
% of total revenues		13.7%		25.6%		25.7%
Online marketing fees	$	35,813	$	41,663	$	45,648		16.3%		9.6%
% of total revenues		31.8%		24.4%		20.3%
Other marketing	$	6,158	$	6,356	$	7,655		3.2%		20.4%
% of total revenues		5.5%		3.7%		3.4%
Total marketing expense	$	57,389	$	91,721	$	111,018		59.8%		21.0%
% of total revenues		50.9%		53.7%		49.4%

Marketing expenses for the year ended December 31, 2011 increased $19.3 million compared to the same period in 2010. The $14.0 million increase in brand marketing relates primarily to a $17.4 million incremental investment in swoodoo, KAYAK Europe and checkfelix.com. Additionally, our online marketing expense

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increased by $4.0 million. As a percentage of revenue, marketing expenses decreased to 49.4% from 53.7% primarily due to efficiencies achieved in US marketing spend during 2011, as compared to the same period in 2010. We believe these marketing investments were the primary contributor to our 41.7% increase in query growth in 2011 as compared to 2010.

Marketing expense for the year ended December 31, 2010 increased $34.3 million compared to the same period in 2009 primarily due to the initial launch of our KAYAK brand marketing campaign. We initiated a brand marketing campaign in November 2009, and for the year ended December 31, 2010, we incurred $39.0 million in KAYAK brand marketing expense. We expect to continue to invest in brand marketing going forward, as we are focused on increasing awareness of our brand and bringing more people to our websites and mobile applications.

Personnel

Personnel costs consist of wages and benefits paid to our employees, stock-based compensation charges and payroll taxes and recruiting costs. Stock-based compensation is a significant portion of our wage and benefit structure and generally increases as we hire additional people. Many other factors can impact the total stock-based compensation expense, including the strike price, volatility and expected life of the options, among other things. Please see the notes to our consolidated financial statements included elsewhere in this prospectus for more information on our stock options. In October 2010, we issued approximately two million options to existing employees and as such, expect stock-based compensation expense to increase significantly as those options vest over the next four years.

	Year ended December 31,						% increase
	(Dollar amounts in thousands)								% increase 2010 to 2011
	2009		2010		2011		2009 to 2010
Salaries, benefits and taxes	$	17,473	$	21,261	$	28,358		21.7%		33.4%
% of total revenues		15.5%		12.5%		12.6%
Stock-based compensation	$	5,165	$	8,503	$	12,427		64.6%		46.1%
% of total revenues		4.6%		5.0%		5.5%
Total personnel	$	22,638	$	29,764	$	40,785		31.5%		37.0%
% of total revenues		20.1%		17.4%		18.2%

Our salaries, benefits and taxes increased primarily due to wage increases for existing employees and a headcount increase of 11 employees as of December 31, 2011 compared to December 31, 2010. In 2011 we also awarded bonuses totaling $1.3 million to our cofounders as discussed in “Executive Compensation”. Stock compensation expense increased in 2011 compared to 2010 due to the additional grant of options to purchase 1,165,000 shares of our common stock and the increase in the fair market value of our common stock.

Salaries, benefits and taxes increased primarily due to a headcount increase of 40 employees between December 2009 and December 2010. Stock-based compensation increased in 2010 compared to 2009, due to the grant of 4,199,590 additional common stock options.

Other general and administrative expenses

All other operating costs are classified as other general and administrative expenses. The largest items in this category of expenses are legal and accounting fees, technology costs, provision for doubtful accounts and facilities expenses. In 2009, general and administrative costs also included $0.3 million of stock-based compensation expense.

	Year ended December 31,						% increase 2009 to 2010			% increase 2010 to 2011
	(Dollar amounts in thousands)
	2009		2010		2011
Other general and administrative expenses	$	6,568	$	9,967	$	16,400		51.8	%		64.5	%
% of total revenues		5.8%		5.8%		7.3%

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Other general and administrative expenses increased $6.4 million for the year ended December 31, 2011 compared to the same period in 2010 primarily due to a $2.9 million increase in legal and accounting fees, a $1.2 million increase in technology costs, and a $0.8 million increase in travel expenses. Legal and accounting fees increased due to activities associated with the formation of our European entity and litigation matters described in “Business — Legal Proceedings”.

Other general and administrative expenses increased $3.4 million from 2009 to 2010 primarily due to $1.5 million in acquisition-related and other legal and accounting fees, $1.2 million from the inclusion of swoodoo results beginning May 2010, and a $0.4 million increase in the provision for doubtful accounts.

Depreciation and amortization

Depreciation and amortization consists primarily of depreciation of computer equipment, software and website development and amortization of our trade names, customer relationships and other intangible assets.

	Years ended December 31,						% increase 2009  to 2010		%  increase (decrease) 2010 to 2011
	(Dollar amounts in thousands)
	2009		2010		2011
Amortization	$	3,328	$	4,619	$	6,566		38.8%		42.2 %
% of total revenues		3.0%		2.7%		2.9%
Depreciation	$	2,052	$	2,202	$	1,920		7.3%		(12.8)%
% of total revenues		1.8%		1.3%		0.9%
Total depreciation and amortization	$	5,380	$	6,821	$	8,486		26.8%		24.4 %
% of total revenues		4.8%		4.0%		3.8%

Depreciation and amortization increased $1.7 million during the year ended December 31, 2011, compared to the same period in 2010. The increase is primarily due to a $2.2 million increase in amortization and depreciation from acquired entities, partially offset by a $0.6 million decrease from SideStep assets that are now fully depreciated.

The inclusion of swoodoo in our results from May 2010 accounted for the $1.4 million increase in depreciation and amortization for the year ended December 31, 2010, compared to the same period in 2009.

Impairment of intangible assets

In January 2011, we determined that we would no longer support two brand names and URLs in the United States and decided to migrate all traffic from sidestep.com to KAYAK.com, resulting in a $15.0 million impairment charge.

Other income (expense)

For the year ended December 31, 2011, we recorded a gain of $1.1 million related to our obligation to buy back shares of our common stock issued in connection with our acquisition of swoodoo in May 2010. We also recorded a $0.8 million gain related to the re-measurement of intercompany balances denominated in foreign currencies.

During 2010, we recorded a gain of $2.9 million related to our obligation to buy back shares of our common stock issued in connection with our acquisition of swoodoo in May 2010. In addition, we realized a gain of $0.5 million related to the sale of the TravelPost assets.

In 2009, we incurred a $1.0 million loss on the early extinguishment of debt.

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Income tax expense (benefit)

Prior to December 31, 2009, we recorded a full valuation allowance against our net deferred tax assets, which consisted primarily of net operating loss carryforwards, due to the uncertainty of our ability to realize those assets. As such, we had nominal income tax expense. On December 31, 2009, we determined that it was more likely than not that we would be able to realize these assets and reversed the valuation allowance, resulting in a tax benefit for that year. In 2010, we incurred income tax expense of $12.1 million, including a $1.6 million increase to the valuation allowance, giving us an effective tax rate of 60.1%. In 2010, we incurred income tax expense of $12.1 million, resulting in an effective tax rate of 60.1%. Key effective tax rate drivers specific to 2010 were the sale of Travelpost, Inc., and an increase to the valuation allowance for state net operating losses incurred when we reduced our presence in California. In 2011, we incurred income tax expense of $6.7 million giving us an effective tax rate of 40.8%. The primary differences between the statutory rate and our effective tax rate include stock compensation from incentive stock options, state tax expense and differences in jurisdictional tax rates, as shown in the table below.

Provisions for income taxes compared with income taxes based on the federal statutory tax rate of 35% were as follows:

	December 31,
	2009			2010			2011
U.S. Statutory federal income tax rate		35.0	%		35.0	%		35.0	%
State income taxes, net of federal benefits		15.8	%		8.3	%		7.2	%
Compensation related to incentive stock options		27.0	%		7.1	%		6.0	%
Gain on sale of TravelPost		—			4.4	%		—
Mark-to-market adjustments		5.7	%		(4.8	)%		(2.6	)%
Change to valuation allowance		(149.1	)%		8.0	%		—
Foreign rate differential		—			—			(2.7	)%
Other		(1.5	)%		2.1	%		(2.1	)%
Effective income tax rate		(67.1	)%		60.1	%		40.8	%

Quarterly Financial Data/Seasonality

The following table presents unaudited consolidated financial data for the trailing eight quarters ended December 31, 2011. The operating results are not necessarily indicative of the results for any subsequent quarter.

	2010 Quarters ended									2011 Quarters ended
	Mar 31			June 30		Sept 30		Dec 31		Mar 31			June 30		Sept 30		Dec 31
Revenues	$	36,745		$	43,721	$	47,814	$	42,418	$	52,674		$	56,753	$	61,160	$	53,947
Cost of revenues (excludes depreciation and amortization)		4,048			3,772		3,810		4,000		4,945			4,684		4,151		4,818
Selling, general, and administrative
Marketing		23,809			21,962		23,368		22,582		28,457			30,025		28,935		23,601
Personnel		6,615			7,101		7,271		8,777		10,039			9,800		10,286		10,660
Other general and administrative expenses		1,543			2,260		2,728		3,436		4,217			4,164		3,196		4,823
Total selling, general and administrative expenses (excludes depreciation and amortization)		31,967			31,323		33,367		34,795		42,713			43,989		42,417		39,084
Depreciation and amortization		1,367			1,660		1,896		1,898		2,061			2,341		1,935		2,149
Impairment of intangible assets		—			—		—		—		14,980			—		—		—
Income (loss) from operations	$	(637	)	$	6,966	$	8,741	$	1,725	$	(12,025	)	$	5,739	$	12,657	$	7,896

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Seasonal factors cause our profitability to fluctuate from quarter to quarter. Typically, our highest revenue quarters are the second and third quarters due to the fact that high travel seasons fall in these quarters. Additionally, our brand marketing expense fluctuates by quarter, and we invest in advance of high travel seasons, with our lightest spend in the third quarter. As a result of the above two factors, our operating income is typically highest in the second and third quarters.

In January 2011, we determined that we would not support two brand names and URLs in the United States and decided that we would migrate all traffic from sidestep.com to KAYAK.com. As a result, our SideStep brand name and URL intangible assets were impaired and we incurred a related impairment charge of $15.0 million in the first three months of 2011.

Acquisitions

In May 2010, in an effort to expand our European operations, we acquired all of the outstanding stated share capital of swoodoo in exchange for $6.8 million in cash, net, and 825,000 shares of our common stock. Pursuant to an option agreed to with the former swoodoo stockholders, in August 2011 we repurchased 685,219 of these shares at a price of €13.33 per share for a total of $13.1 million. We are no longer obligated to repurchase any additional shares.

In April 2011, we acquired all of the outstanding shares of JaBo Vertrieb-und Entwicklung GmbH, or JaBo Software, for $9.2 million in cash, net. JaBo Software operates checkfelix.com, a leading travel metasearch website in Austria.

Liquidity and Capital Resources

We have primarily funded our operations through the issuance of equity securities and cash flows from operations. Early in our history, we relied on cash provided from the sale of shares of our redeemable convertible preferred stock to fund our operations and raised $29.8 million prior to 2007. In 2007, we raised another $165.7 million through the sale of preferred stock and entered into $30.0 million of term loans to fund our acquisition of SideStep.

We began to generate cash flows from operations in late 2007 and have not required any additional financing to fund our operations. We repaid all outstanding principal and interest on the term loans in early 2009. We use our cash to fund operations, make capital expenditures and acquire complementary businesses from time to time. We also have not recorded U.S. income and foreign withholding taxes on the earnings of our foreign subsidiaries at December 31, 2011, because we intend to permanently reinvest those earnings.

As of December 31, 2011, we had cash and cash equivalents and marketable securities of $46.3 million that we expect to utilize, along with operating cash flows, to fund brand marketing, expansion in Europe and general corporate purposes. Included in this amount is $3.6 million of cash held by foreign subsidiaries that is not available to fund domestic operations and obligations without paying taxes upon its repatriation. Our operations currently provide us with most of our liquidity needs, and at this time we have nominal capital expenditure requirements. Our known material liquidity needs for periods beyond the next twelve months are described in “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Contractual Obligations”. We believe that cash from operations, together with our cash and short-term investment balance are sufficient to meet our ongoing capital expenditures, working capital requirements and other capital needs for at least the next twelve months.

Our liquidity could be negatively affected by a decrease in demand for our products and services. In addition, we may make acquisitions complementary to our business and may need to raise additional capital through future debt or equity financing to provide for greater flexibility to fund any such acquisitions. Additional financing may not be available at all or on terms favorable to us.

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The following table presents cash flow information for the stated periods:

	Year ended December 31,
	2009			2010			2011
	(Dollar amounts in thousands)
Cash flows from operating activities	$	12,616		$	21,932		$	32,899
Cash flows from investing activities		6,964			(8,375	)		(33,848	)
Cash flows from financing activities		(27,239	)		5,737			1,809

Cash flows from operating activities

Cash flows from operating activities were $32.9 million for the year ended December 31, 2011 as compared to cash flows from operating activities of $21.9 million for the year ended December 31, 2010, an increase of $11.0 million. The increase in operating cash flows is primarily related to cash from working capital of $2.6 million as of December 31, 2011 as compared to cash used for working capital of $5.4 million as of December 31, 2010. The change in cash from working capital relates primarily to an increase in payables. Non-cash charges increased to $20.6 million for the year ended December 31, 2011 from $19.3 million for the year ended December 31, 2010, primarily due to a decrease in SideStep deferred tax liabilities. Net income also increased to $9.7 million in 2011 from $8.0 million in 2010.

Cash flows from operating activities were $21.9 million and $12.6 million in 2010 and 2009, including net income of $8.0 million and $6.9 million, respectively. The difference in net income was offset by non-cash charges, which were $10.7 million higher in 2010 than in 2009, primarily due to changes in net deferred tax assets, stock based compensation, and amortization from swoodoo intangible assets acquired in May 2010. Cash used for working capital was $5.4 million for 2010 as compared to $2.9 million in 2009, due to an increase in our accounts receivable, partially offset by accrued expenses. As of December 31, 2010 and 2009, accounts receivable, net were $30.2 million and $18.7 million, respectively, and the majority of this increase was due to an increase in sales over the same period. The increase in accrued expenses is primarily attributable to increases in tax, marketing, and technology related accruals for the year ended December 31, 2010.

Cash flows from investing activities

Cash used in investing activities was $33.8 million and $8.4 million for the years ended December 31, 2011 and 2010, respectively. The year ended December 31, 2011 included $13.2 million in cash used to repurchase shares related to the acquisition of swoodoo in 2010. Cash used in investing activities included the net purchase of $7.2 million in marketable securities in 2011, an increase of $4.3 million from 2010. Cash used for business combinations was $9.2 million in 2011 as compared to $6.8 million in 2010 as discussed in “—Acquisitions” and the notes to our consolidated financial statements.

Cash used in investing activities was $8.4 million for the year ended December 31, 2010 compared to cash provided by investing activities of $7.0 million in 2009. Capital expenditures were $2.3 million in 2010 and 2009. During 2010, we had net purchases of marketable securities of $2.9 million, while in 2009 we had net sales of marketable securities of $9.2 million. In 2009, we sold marketable securities to generate cash used to pay down our term debt. During 2010, we acquired swoodoo for $6.8 million in cash, net, and received $3.6 million in cash from our sale of TravelPost.

Cash flows from financing activities

Cash provided by financing activities was $1.8 million for the year ended December 31, 2011 as compared to $5.7 million for the year ended December 31, 2010. Proceeds and tax benefits from the exercise of stock options increased to $3.3 million in 2011 from $0.7 million in 2010. Cash used in connection with the initial

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public offering during 2011 was $1.5 million. The year December 31, 2010 included proceeds of $3.7 million from the repayment of shareholder loans and proceeds of $1.4 million from the exercise of common stock warrants.

Cash provided by financing activities was $5.7 million for the year ended December 31, 2010 compared to cash used for financing activities of $27.2 million for the same period in 2009. The difference was due primarily to $25.3 million used to pay off term loans in 2009. Additionally, in 2009, we provided loans to our shareholders of $2.5 million. These loans, plus earlier loans, were repaid in 2010, resulting in cash proceeds of $3.7 million.

Contractual Obligations

Our contractual obligations as of December 31, 2011 were as follows:

	Amounts due by period (Dollar amounts in thousands)
	Total		Less than 1 year		1-3 years		3-5 years		More than 5 years
Operating lease obligations	$	6,301	$	1,697	$	2,228	$	1,841	$	535
Content licensing and technology agreements	$	7,000	$	7,000	$	—	$	—	$	—
Total contractual cash obligations	$	13,306	$	8,697	$	2,228	$	1,841	$	535

We lease our office and data center facilities under noncancelable leases that expire at various points through January 2016. See “Business—Facilities” for further discussion of our leased premises. We are also responsible for certain real estate taxes, utilities and maintenance costs on our office facilities. In addition, we have various content licensing and technology agreements that, if renewed, will continue to incur costs in future periods.

Off-Balance Sheet Obligations

We had no off-balance sheet obligations as of December 31, 2011.

Critical Accounting Policies and Estimates

We prepare our Consolidated Financial Statements in accordance with accounting principles generally accepted in the U.S. To do so we make estimates and assumptions that affect our reported amounts of assets, liabilities, revenues and expenses, as well as related disclosure of contingent assets and liabilities. In some cases, we could reasonably have used different accounting policies and estimates. In addition, changes in the accounting estimates are reasonably likely to occur from period to period. Accordingly, actual results could differ materially from our estimates. To the extent that there are material differences between these estimates and actual results, our financial condition or results of operations will be affected. We base our estimates on past experience and other assumptions that we believe are reasonable under the circumstances, and we evaluate these estimates on an ongoing basis. We describe our significant accounting policies in Note 2 of our consolidated financial statements found elsewhere in this prospectus. We believe the following critical accounting estimates are the most significant areas of judgments and estimates used to prepare our financial statements.

Revenue Recognition

We generate revenue when we refer a user to a third-party website, either through our query results or through advertising placements on our websites and by facilitating transactions through our websites and mobile applications. We recognize revenue upon completion of the referral, provided that our fees are fixed and determinable, there is persuasive evidence of the arrangement and collection is reasonably assured, as follows:

Distribution Revenues. Revenues are recognized either when a user clicks on a link that refers them to a third-party provider or when the user completes a purchase with the third party provider, depending on terms of

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the contract. For certain hotels and car rental companies revenue is not earned until the user consumes the travel, in which case we recognize the revenue in the period in which the travel was consumed. Generally, we receive travel consumption reports from travel suppliers and OTAs on a monthly basis which report in detail travel consumed in the immediately prior month.

Advertising Revenues. Revenues are recognized when a user clicks on an advertisement that a customer has placed on our website or when we display an advertisement, regardless of whether the user clicks on the advertisement.

Stock-Based Compensation

Our stock-based compensation expense is estimated at the grant date based on an award’s fair value as calculated by the Black-Scholes option-pricing model and is recognized as expense over the requisite service period. The Black-Scholes model requires various highly judgmental assumptions including expected volatility and option life. If any of the assumptions used in the Black-Scholes model changes significantly, stock-based compensation expense may differ materially in the future from that recorded in the current period. In addition, we are required to estimate the expected forfeiture rate and only recognize expense for those shares expected to vest. We estimate the forfeiture rate based on historical experience. To the extent our actual forfeiture rate is different from our estimate, stock-based compensation expense is adjusted accordingly. Please see Note 13 to our consolidated financial statements found elsewhere in this prospectus for further information regarding our stock-based compensation.

Common Stock Valuations

For all option grants, the fair value of the common stock underlying the option grants was determined by our board of directors, with the assistance of management. The board of directors and management intended all options granted to be exercisable at a price per share not less than the per share fair value of our common stock underlying those options on the date of grant.

To make our estimates, we utilize guidance set forth in the 2004 AICPA Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, or the AICPA Guide. We recognize that the value of our stock changes between valuations and as such, consider other factors when determining the fair value of our stock for the purposes of determining stock compensation expense, such as:

Sales of our Common Stock. Sales of our common stock can be a strong indicator of the value of our stock, but do not necessarily determine the value. We consider the volume of shares sold in the transaction, the circumstances of the sale and the sophistication and independence of the buyer in order to determine whether or not the sale indicates a new fair value of our common stock.

Sales of our Convertible Preferred Stock. Sales of our convertible preferred stock can assist in estimating the fair value of our common stock. In order to determine the fair value of common after a sale of convertible preferred stock, we consider the volume of shares sold, circumstances of the sale, independence of the buyers and the value of the preferential rights associated with the class of convertible preferred stock sold.

Specific Events at KAYAK. In addition to the above factors, we consider significant events at KAYAK that may have impacted our value, such as launch of a new product, signing a significant new customer, significant change in management team, etc.

The following sets forth our option grants between January 1, 2009 and July 31, 2011, and discusses our methodology to determine the fair value of our common stock at each grant date.

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In 2009, we issued options to purchase shares of our common stock at the following exercise prices:

Grant Date	Options Granted		Exercise Price		Fair Value of Common Stock		Intrinsic Value
February 26, 2009		265,000	$	15.50	$	7.50	$	—
May 19, 2009		535,000	$	7.50	$	7.50	$	—
July 7, 2009		2,044,000	$	7.50	$	7.50	$	—
July 22, 2009		170,000	$	7.50	$	7.50	$	—
November 13, 2009		255,000	$	7.50	$	11.29	$	3.79

In February 2009, the board of directors determined the fair value of our common stock to be $15.50 based on the last sale of 626,664 shares of our common stock to an independent third party in April 2008. The purchaser of the stock was a sophisticated investor with no previous ownership in our company and which performed adequate due diligence to determine a fair value of $15.50 per share. There were no other significant transactions in our stock from April 2008 to February 2009 and as a result, the board of directors believed that this sale best represented the fair value of our common stock on that date. There was no significant change in our operating results or forecasts during this time period.

In early 2009, we estimated the fair value of our common stock as of December 31, 2008 using the market approach and the income approach, in order to assist the board of directors in assigning an exercise price to future stock grants. We believe both of these approaches were appropriate methodologies given our stage of development at that time. For the market approach, we utilized the guideline company method by analyzing a population of comparable companies and selected those technology companies that we considered to be the most comparable to us in terms of product offerings, revenues, margins and growth. We then used these guideline companies to develop relevant market multiples and ratios, which were applied to our corresponding financial metrics to estimate our total enterprise value. We relied on the following key assumptions for the market approach:

• our projected revenues determined as of the valuation date based on our estimates; and

• multiples of market value to expected future revenues, determined as of the valuation date, based on a group of comparable public companies. This group of comparable public companies includes companies in four categories: online travel, e-commerce, advertising and recent IPOs. We select companies from these categories that are similar to us in at least one of the following areas: size, growth, liquidity, profitability and leverage.

For the income approach, we performed discounted cash flow analyses which utilized projected cash flows as well as a residual value, which were then discounted to the present value in order to arrive at our current equity value to arrive at an enterprise value. We relied on the following key assumptions for the income approach in addition to the management projections discussed above:

• discount rate applied to forecasted future cash flows to calculate the present value of those cash flows; and

• terminal value multiple applied to our last year of forecasted cash flows to calculate the residual value of our future cash flows.

In determining our enterprise value, we applied equal weighting to market and income approaches, as the indicated equity value under the scenarios was reasonably similar. In allocating the total enterprise value between preferred and common stock, we considered the liquidation preferences of the preferred stockholders and utilized the option-pricing method, or OPM, for calculating a range of values for the common stock, based on the likelihood of various liquidity scenarios. The OPM utilized a volatility factor of 80% based on the peer group above and applied a lack of marketability discount of 20%. We assumed a 30% likelihood of an initial public offering within one year, 10% likelihood of a strategic sale and 60% likelihood of remaining as a private company, which produced an indicated value of our common stock of $6.50—$8.48. We then chose the midpoint of the range to arrive at a common stock value of $7.50. This value was significantly lower than our last

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indicated value due to an overall decrease in public company comparable multiples of 50%, as well as to our lowered forecasted revenues and cash flows as a result of the poor economy.

Based on the results of the appraisal, the board of directors determined that the fair value of our common stock was $7.50 per share. There were no significant transactions involving our common stock or convertible preferred stock during 2009. On July 7, 2009, we entered into amended stock option agreements with certain of our employees pursuant to which we decreased the exercise price on options to purchase 2,044,000 shares of our common stock to $7.50 per share. In consideration for the lower exercise price these employees also agreed to restart the vesting of the options as of July 7, 2009.

During the fourth quarter of 2009, we increased our forecasted revenue and cash flows due to a strengthening in our results. Accordingly, we performed an updated valuation of our company as of October 31, 2009. This valuation again calculated an overall enterprise value, but relied on the income approach to calculate the value, as we believed that it best considered our expected high growth and profitability. The market approach was used to validate the results of the income approach, but no weight was assigned to it. In performing our calculations, we relied upon the methodologies described above as of October 31, 2009, however, with respect to our application of the market approach we used a multiple of projected EBITDA instead of revenues due to our recent demonstration of profitability.

The enterprise value was then allocated to the various classes of our stock using the OPM and applying a 70% volatility factor and 40% likelihood of an initial public offering within 12 months. We then applied a 20% discount to the value due to lack of marketability to arrive at an estimated fair value of our common stock of $11.29, which the board used to determine the exercise price of future stock option grants.

In 2010, we issued options to purchase shares of our common stock at the following exercise prices:

Grant Date	Options Granted		Exercise Price		Fair Value of Common Stock		Intrinsic Value
February 11, 2010		325,000	$	11.29	$	11.29	$	—
April 29, 2010		1,075,000	$	13.00	$	13.00	$	—
July 22, 2010		205,000	$	13.00	$	14.82	$	1.82
October 7, 2010		140,000	$	14.82	$	17.60	$	2.78
October 20, 2010		2,079,590	$	14.82	$	17.60	$	2.78
October 21, 2010		40,000	$	15.50	$	17.60	$	2.10
November 15, 2010		110,000	$	16.50	$	17.60	$	1.10
December 8, 2010		235,000	$	16.50	$	17.60	$	1.10

On March 22, 2010, an independent third party investor purchased 769,230 shares of common stock (2.32% of outstanding common equivalents at that time) from existing investors at a price of $13.00 per share. The investor is an institutional investor who previously had no shares in KAYAK and who conducted appropriate due diligence. There were no other significant transactions involving our common stock or convertible preferred stock or significant changes to our business between March 22, 2010 and July 22, 2010. The board of directors concluded that this transaction established the fair value of our common stock which was the best representation of our common stock value at April 29, 2010.

We prepared a revised valuation as of July 31, 2010 and utilized the probability weighted expected return method, or PWERM, approach to allocate value to our common shares. The PWERM approach employs various market approach and income approach calculations depending upon the likelihood of a given liquidation scenario and we believed it to be appropriate given our preparations for an initial public offering. We assumed that there was a 40% likelihood of an initial public offering by mid-May 2011, a 30% probability of a strategic sale and 30% likelihood of remaining a private company. We calculated values under each scenario using financial projections as of July 31, 2010 as follows:

Initial Public Offering:

• utilized the market approach using the same peer group for comparison as in the October 31, 2009 valuation;

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• applied a one-year forward multiple to projected revenues determined as of the valuation date;

• arrived at an implied share price of $25.81 assuming conversion of all convertible preferred stock to common stock; and

• applied a discount for lack of marketability of shares of 17% and discounted the value back to present value using a discount rate of 22% to arrive at a per share price of $18.42.

Strategic Sale:

• utilized the market approach using the same peer group for comparison as in the October 31, 2009 valuation;

• applied a multiple to trailing twelve months revenue based on recent representative transactions;

• arrived at an implied enterprise value at the sale and allocated value to various classes of stock based on whether we believed those shares would convert to common stock or remain as convertible preferred stock; and

• applied a discount for lack of liquidity of 3% and discounted the value back to present value using a discount rate of 22% to arrive at a price per common share of $14.72.

Remain as Private Company:

• utilized the income approach and a discount rate of 22% to calculate the present value of expected future cash flows to arrive at an enterprise value; and

• allocated the enterprise value to various classes of shares using the OPM model using a volatility of 48.68% and applied a discount for lack of marketability of 33% to arrive at a price per common share of $10.11.

We then applied the probabilities of each liquidity scenario to their respective price per common share to arrive at a value per common share of $14.82.

The board of directors approved the issuance of options to purchase our common stock on September 17, 2010 using the fair value established by our valuation. The number of options approved exceeded the amount of available shares in our pool and as a result, we could not grant the options until the pool was increased. Because of the delay in communicating the grants to our employees, the options had a grant date of October 20, 2010. Because the grant date was so much later than the date at which the options were approved and because the possibility of an initial public offering or other liquidity event was increasingly likely, we determined that we should prepare a revised appraisal as of the grant date, which was completed in January 2011.

This valuation was performed using the same methodology as described above for our July 31, 2010 valuation; however, given our preparations for a potential initial public offering, the likelihood of an initial public offering scenario increased to 60%, while the probabilities of a strategic sale or remaining as a private company were each assumed to be 20%. We calculated values under each scenario using financial projections as of October 31, 2010 as follows:

Initial Public Offering:

• utilized the market approach, but expanded the peer group to include more companies in e-commerce and media, along with technology companies that recently completed initial public offerings;

• applied a 1.5 year forward multiple of EBITDA determined as of the valuation date;

• arrived at an implied share price of $25.69 assuming conversion of all convertible preferred stock to common stock; and

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• applied a discount for lack of marketability of shares of 13% and discounted the value back to present value using a discount rate of 19% to arrive at a per share price of $20.34.

Strategic Sale:

• utilized the market approach and applied a multiple to trailing twelve months revenue based on recent representative transactions;

• arrived at an implied enterprise value at the sale and allocated value to various classes of stock based on whether we believed those shares would convert to common stock or remain as convertible preferred stock; and

• applied a discount for lack of liquidity of 3% and discounted the value back to present value using a discount rate of 19% to arrive at a price per common share of $15.76.

Remain as a Private Company:

• utilized the income approach and a discount rate of 19% to calculate the present value of expected future cash flows to arrive at an enterprise value; and

• allocated the enterprise value to various classes of shares using the OPM model using a volatility of 59.45% and applied a discount for lack of marketability of 33% to arrive at a price per common share of $11.22.

We then applied the probabilities of each scenario to their respective price per common share to arrive at a value per common share of $17.60.

In 2011, we issued options to purchase shares of our common stock at the following exercise prices:

Grant Date	Options Granted		Exercise Price		Fair Value of Common Stock		Intrinsic Value
January 25, 2011		10,000	$	17.60	$	17.60	$	—
March 2, 2011		70,000	$	20.00	$	20.00	$	—
June 7, 2011		690,000	$	21.00	$	21.00	$	—
August 16, 2011		145,000	$	25.50	$	25.50	$	—
October 4, 2011		65,000	$	25.50	$	25.50	$	—
December 14, 2011		175,000	$	20.14	$	20.14	$	—

We estimated the fair value of our stock at January 25, 2011 using the valuation prepared as of October 31, 2010. There were no significant transactions involving our stock between October 31, 2010 and January 25, 2011 that caused us to believe that this valuation was not still accurate.

Concurrent with the grant of options on March 2, 2011, we prepared a revised valuation of our common stock. The valuation was performed using the same methodology as at October 31, 2010; however, given our preparations for a potential IPO we increased the likelihood of an IPO scenario to 85%, while the probabilities of a strategic sale or remaining as a private company were assumed to be 10% and 5%, respectively. We calculated values under each scenario using financial projections as of January 31, 2011 as follows:

Initial Public Offering:

• utilized the market approach, with a peer group that included companies in travel and advertising, e-commerce and media, along with technology companies that recently completed IPOs;

• applied a 1.5-year forward multiple of EBITDA determined as of the valuation date;

• arrived at a marketable, minority value of $22.96 per share; and

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• applied a discount for lack of marketability of shares of 8% and discounted the value back to present value using a discount rate of 17% to arrive at a per share price of $20.44.

Strategic Sale:

• utilized the market approach and applied a multiple to trailing twelve months revenue based on recent representative transactions;

• arrived at an implied enterprise value at the sale and allocated value to various classes of stock based on whether we believed those shares would convert to common stock or remain as convertible preferred stock; and

• applied a discount for lack of liquidity of 3% and discounted the value back to present value using a discount rate of 17% to arrive at a price per common share of $18.75.

Remain as a Private Company:

• utilized the income approach and a discount rate of 17% to calculate the present value of expected future cash flows to arrive at an enterprise value; and

• allocated the enterprise value to various classes of shares using the OPM model using a volatility of 55.4% and applied a discount for lack of marketability of 29% to arrive at a price per common share of $12.24.

We then applied the probabilities of each scenario to their respective price per common share to arrive at a value per common share of $19.86.

When determining the fair value of our common stock, management and the board of directors considered not only the valuation analysis, but also an offer from one of our investors to purchase a significant number of shares of common stock from another of our shareholders at a price of $20.00. Although the sale was not ultimately consummated, management and the board of directors considered the offer price to be representative of the fair value of our stock as validated by the valuation.

Prior to the grant of options on June 7, 2011, we prepared a revised valuation of our common stock. The valuation was performed using the same methodology as was used previously; however, given various uncertainties surrounding our IPO, we decreased the likelihood of the IPO scenario to 50%, while the probabilities of a strategic sale or remaining as a private company were assumed to be 20% and 30%, respectively. We calculated values under each scenario using financial projections as of April 30, 2011 as follows:

Initial Public Offering:

• Utilized the market approach, with a peer group that included companies in travel and advertising, ecommerce and media, along with technology companies that recently completed IPOs;

• Applied a 1.5 year forward multiple of EBITDA determined as of the valuation date;

• Arrived at a marketable, minority value of $27.97 per share; and

• Applied a discount for lack of marketability of shares of 7% and discounted the value back to present value using a discount rate of 16% to arrive at a per share price of $24.30.

Strategic Sale:

• Utilized the market approach and applied a multiple to trailing twelve months revenue based on recent representative transactions;

• Arrived at an implied enterprise value at the sale and allocated value to various classes of stock based on whether we believed those shares would convert to common stock or remain as convertible preferred stock; and

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• Applied a discount for lack of liquidity of 19% and discounted the value back to present value using a discount rate of 16% to arrive at a price per common share of $20.24.

Remain as a Private Company:

• Utilized the income approach and a discount rate of 16% to calculate the present value of expected future cash flows to arrive at an enterprise value; and

• Allocated the enterprise value to various classes of shares using the OPM model using a volatility of 56.7% and applied a discount for lack of marketability of 23% to arrive at a price per common share of $15.71.

We then applied the probabilities of each scenario to their respective price per common share to arrive at a value per common share of $20.91.

When determining the fair value of our common stock, management and the board of directors considered not only the valuation analysis, but also recent sales of our stock to current investors. On April 20, 2011, an individual who was not an employee of the Company sold 201,409 shares of common stock, 173,591 shares of Series A Preferred Stock and 225,000 shares of Series B-1 Preferred Stock to an existing investor at $17.75 per share. On May 13 and May 20, 2011, two Company executives sold a total of 400,000 shares of Series A Preferred Stock for $21.00 per share to an existing investor.

Based on the valuation, recent significant sales of stock and knowledge of our financial performance and condition, the board of directors determined the value of our common stock to be $21.00 per share.

With respect to stock options granted on August 16, 2011 and on October 4, 2011, our board of directors considered our financial projections, current market conditions, plans for an IPO and input from our advisors to arrive at a fair market value of $25.50 per share.

Prior to the stock option grant on December 14, 2011, we prepared a revised valuation of our common stock. The valuation was performed using the same methodology as was used previously; however, we increased the likelihood of the IPO scenario to 75%, while the probabilities of a strategic sale or remaining as a private company were assumed to be 20% and 5%, respectively. We calculated values under each scenario using financial projections as of October 31, 2011 as follows:

Initial Public Offering:

• Utilized the market approach, using the same peer group as in prior valuations, adjusting to include more companies that recently completed IPOs;

• Applied a 1.5 year forward multiple of EBITDA determined as of the valuation date; and

• Applied a discount for lack of marketability of shares of 7% and discounted the value back to present value using a discount rate of 15% to arrive at a price per common share of $20.49.

Strategic Sale:

• Utilized the market approach and applied a multiple to trailing twelve months revenue based on recent representative transactions;

• Arrived at an implied enterprise value at the sale and allocated value to various classes of stock based on whether we believed those shares would convert to common stock or remain as convertible preferred stock; and

• Applied a discount for lack of liquidity of 15% and discounted the value back to present value using a discount rate of 15% to arrive at a price per common share of $20.34.

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Remain as a Private Company:

• Utilized the income approach and a discount rate of 15% to calculate the present value of expected future cash flows to arrive at an enterprise value; and

• Allocated the enterprise value to various classes of shares using the OPM model with a volatility of 53% and applied a discount for lack of marketability of 22% to arrive at a price per common share of $14.08.

We then applied the probabilities of each scenario to their respective price per common share to arrive at a value per common share of $20.14. On December 14, 2011, the board of directors approved the grant of options to purchase shares of our common stock using the fair value established by this valuation.

For the period from January 1, 2012 through April 10, 2012, we have issued options to purchase shares of our common stock at the following exercise prices:

Grant Date	Options Granted		Exercise Price		Fair Value of Common  Stock		Intrinsic Value
February 7, 2012		85,000	$	20.14	$	20.14	$	—
April 10, 2012		378,000	$	25.50	$	25.50	$	—

The board of directors approved the issuance of options to purchase our common stock on February 7, 2012 using the fair value established by the valuation performed as of October 31, 2011. There were no significant transactions involving our stock between October 31, 2011 and February 7, 2012 that caused us to believe that this valuation was not still accurate.

We again performed a valuation of our common stock in late March 2012. The valuation was performed using the same methodology as was used previously; however, we increased the likelihood of the IPO scenario to 85%, while the probabilities of a strategic sale or remaining as a private company were 10% and 5%, respectively. We calculated values under each scenario using financial projections as of February 29, 2012 as follows:

Initial Public Offering:

• Utilized the market approach, using the same peer group as in prior valuations, adjusting to include more companies that recently completed IPOs;

• Applied a 1.5 year forward multiple of EBITDA determined as of the valuation date; and

• Applied a discount for lack of marketability of shares of 8% and discounted the value back to present value using a discount rate of 13% to arrive at a price per common share of $23.40.

Strategic Sale:

• Utilized the market approach and applied a multiple to trailing twelve months EBITDA based on recent representative transactions;

• Arrived at an implied enterprise value at the sale and allocated value to various classes of stock based on whether we believed those shares would convert to common stock or remain as convertible preferred stock; and

• Applied a discount for lack of liquidity of 14% and discounted the value back to present value using a discount rate of 13% to arrive at a price per common share of $22.00.

Remain as a Private Company:

• Utilized an equal weighting of the income approach and a discount rate of 13% and the market multiple approach based on trailing twelve month revenue to calculate the present value of expected future cash flows to arrive at an enterprise value; and

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• Allocated the enterprise value to various classes of shares using the OPM model with a volatility of 51% and applied a discount for lack of marketability of 21% to arrive at a price per common share of $19.74.

We then applied the probabilities of each scenario to their respective price per common share to arrive at a value per common share of $23.07. In determining the fair value of our common stock, the board of directors considered current market conditions and our projections, along with the valuation that we performed. Weighing all factors, the board of directors set the fair market value of our common stock on April 10, 2012 at $25.50. Stock options granted on April 10, 2012, were issued with an exercise price equal to this value.

Income Taxes

We are subject to income taxes in the U.S. and some foreign jurisdictions. We use estimates and exercise significant judgment to calculate our deferred taxes, tax from uncertain tax positions, and the overall income tax provision/(benefit). As a result, ultimate settlement of our tax positions may differ from the amounts accrued and may result in an increase or decrease to income tax expense in our results of operations in the future.

Realization of the future tax benefits depends on many factors, including our ability to continue to generate taxable income within the net operating loss carryforward period. Prior to 2009, we did not have sufficient history of generating taxable income to support the assumption that it was more likely than not that future tax benefits would be realized and as such, a full valuation reserve was recorded against the net deferred tax asset. In 2009, based on historical and expected operating results, we determined that it was more likely than not that future tax benefits would be realized and released the valuation allowance of $3.9 million. In 2010, we recorded a valuation allowance against certain state deferred tax assets attributable to net operating losses as a result of a change in our state allocation. There was no significant change to the valuation allowance in 2011.

Our effective tax rate has differed from the statutory rate primarily due to the impact of state taxes, nondeductible stock compensation expense and lower tax rates outside the United States. Our 2011 effective tax rate was 40.8%.

Acquisitions

We account for acquisitions using the purchase method of accounting. In each case, we allocated the purchase price to the assets acquired, including intangible assets and liabilities assumed, based on estimated fair values at the date of the acquisition.

Recoverability of Intangible Assets, Including Goodwill

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. When such events occur, we compare the carrying amounts of the assets to their undiscounted expected future cash flows. If this comparison indicates that there is impairment, the amount of the impairment is calculated as the difference between the carrying value and fair value. Goodwill is tested for impairment at least annually and whenever events or changes in circumstances indicate that goodwill may be impaired. Goodwill represents the excess of the cost of acquired business over the fair value of the assets acquired at the date of acquisition. Based on our most recent annual analysis, we believed that the fair values of our reporting units exceeded their carrying values by a significant amount and therefore no impairment of goodwill was recorded. Our goodwill is not deductible for tax purposes.

JOBS Act

On April 5, 2012, the JOBS Act was signed into law. The JOBS Act contains provisions that, among other things, reduce certain reporting requirements for qualifying public companies. As an “emerging growth company” we have elected under the JOBS Act to delay adoption of new or revised accounting pronouncements

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applicable to public companies until such pronouncements are made applicable to private companies. Additionally, we are in the process of evaluating the benefits of relying on the other reduced reporting requirements provided by the JOBS Act.

Subject to certain conditions set forth in the JOBS Act, if, as an “emerging growth company”, we choose to rely on such exemptions we may not be required to, among other things, (i) provide an auditor’s attestation report on our system of internal controls over financial reporting pursuant to Section 404, (ii) provide all of the compensation disclosure that may be required of non-emerging growth public companies under the Dodd-Frank Wall Street Reform and Consumer Protection Act, (iii) comply with any requirement that may be adopted by the PCAOB regarding mandatory audit firm rotation or a supplement to the auditor’s report providing additional information about the audit and the financial statements (auditor discussion and analysis), and (iv) disclose certain executive compensation related items such as the correlation between executive compensation and performance and comparisons of the CEO’s compensation to median employee compensation. These exemptions will apply for a period of five years following the completion of our initial public offering or until we are no longer an “emerging growth company,” whichever is earlier.

Quantitative and Qualitative Disclosures about Market Risk

We are exposed to market risks in the ordinary course of our business. These risks primarily consist of foreign exchange and interest rate risks.

Foreign Exchange Risk

We transact business in various foreign currencies and have some international revenues and costs which are denominated in foreign currencies. This exposes us to foreign currency risk. At this time, our exposure is immaterial, given that the vast majority of our transactions, income and expenses are in U.S. dollars. If exchange rates were to fluctuate significantly, we would see higher gains or losses from transactions in the “General and Administrative” line of our statement of operations, and larger cumulative translation adjustments in the “Accumulated Other Comprehensive Income” category of our consolidated balance sheet. The volatility of exchange rate is dependent on many factors that we cannot forecast with reliable accuracy. At this time we do not, but we may in the future, enter into derivatives or other financial instruments in an attempt to hedge our foreign currency exchange risk. It is difficult to predict the impact hedging activities would have on our results of operations.

Interest Rate Risk

We invest our excess cash primarily in highly liquid debt instruments of the U.S. government and its agencies, municipalities in the U.S., debt instruments issued by foreign governments, time deposits, money market and other funds, and corporate debt securities. By policy, we limit the amount of credit exposure to any one issuer.

Investments in both fixed rate and floating rate interest earning securities carry a degree of interest rate risk. Fixed rate securities may have their fair market value adversely impacted due to a rise in interest rates, while floating rate securities may produce less income than predicted if interest rates fall. Due in part to these factors, our income from investments may decrease in the future.

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BUSINESS

Overview

We are a technology-driven company committed to improving online travel. Cofounders of Expedia, Travelocity and Orbitz started KAYAK in 2004 to take a better approach to finding travel online. Our websites and mobile applications enable people to easily research and compare accurate and relevant information from hundreds of other travel websites in one comprehensive, fast and intuitive display. We also provide multiple filtering and sorting options, travel management tools and services such as flight status updates, pricing alerts and itinerary management. Once users find their desired flight, hotel or other travel products, KAYAK sends them to their preferred travel supplier or OTA website to complete their purchase, and in many cases, users may now complete hotel bookings directly through our websites and mobile applications.

KAYAK’s services are free for travelers. We offer travel suppliers and online travel agencies, or OTAs, an efficient channel to sell their products and services to a highly targeted audience focused on purchasing travel. We earn revenues by sending referrals to travel suppliers and OTAs and from a variety of advertising placements on our websites and mobile applications.

Since our commercial launch in 2005, KAYAK has experienced significant growth:

• For the year ended December 31, 2011, we generated $224.5 million of revenues, representing growth of 32% over the year ended December 31, 2010;

• For the year ended December 31, 2011, we generated income from operations of $14.3 million as compared to income from operations of $16.8 million for the year ended December 31, 2010. After adjusting for a $15.0 million impairment charge related to our decision to stop supporting the SideStep brand name, operating income for the year ended December 31, 2011 was $29.2 million, a 74% increase over the same period in 2010.

• For the year ended December 31, 2011, we had Adjusted EBITDA of $50.2 million representing growth of 56.2% over the year ended December 31, 2010. Adjusted Earnings Before Interest, Taxes, Depreciation and Amortization, or Adjusted EBITDA, is a non-generally accepted accounting principle metric used by management to measure our operating performance. See “—Summary Consolidated Historical Operating Data” for an additional description of Adjusted EBITDA and a reconciliation of Adjusted EBITDA to income (loss) from operations.

• For the year ended December 31, 2011, we processed 899 million user queries for travel information, representing growth of 42% over the year ended December 31, 2010; and

• KAYAK mobile applications have been downloaded over 13 million times since their introduction in March 2009. For the year ended December 31, 2011, we had 7 million downloads, representing growth of 78% over the year ended December 31, 2010.

As of March 31, 2012, we had 169 employees, and we had local websites in 14 countries outside the U.S., including the United Kingdom, Germany, France, Spain, Italy and Austria.

Our Industry

Market Opportunity

As a distribution and advertising platform, we participate in both the online travel market and the online travel advertising market.

Online Travel: A Large and Growing Market

The travel industry in the U.S., Europe and Asia Pacific accounted for $803 billion in global expenditures in 2010, and is projected to increase at a 6% CAGR through 2012. Online leisure and unmanaged business travel

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spend, or online travel spend, was approximately $247 billion of this amount, or 31%, with this category increasing at a 16% CAGR between 2005 and 2010. We believe that travel, with its research and information intensive nature, real-time pricing, electronic fulfillment capabilities and thousands of travel options, is well-suited for the online channel. Currently, online travel represents the largest category of e-commerce, with total sales exceeding the combined total of electronics, books, software, appliances and collectibles. Online travel spend is projected to increase at a 10% CAGR from 2010 through 2012, growing to represent 33% of total travel purchases in 2012.

The online travel industry is composed of thousands of travel supplier and OTA websites, which compete for travel bookings. In 2010, travel supplier websites accounted for 63% of total online travel bookings, and the remaining 37% was provided by OTAs.

The Global Opportunity

In the U.S., the online travel market increased at a 9% CAGR from 2005 through 2010, reaching $97 billion in 2010, which was 38% of total U.S. travel spend. The U.S. online travel market is projected to grow at an 8% CAGR from 2010 through 2012.

In Europe, the online travel market grew at a 22% CAGR from 2005 through 2010, reaching $97 billion in 2010, which was 33% of total European travel spend. The European online travel market is projected to grow at a 9% CAGR from 2010 through 2012. The U.K., France and Germany collectively represent 67% of the overall European online travel market.

In Asia, the online travel market grew at a 27% CAGR from 2005 through 2010, reaching $53 billion in 2010, which represented 21% of total Asian travel spend. As Internet usage, broadband adoption and online payment capabilities continue to rapidly increase, the Asian online travel market is projected to grow at a 15% CAGR from 2010 through 2012.

Key Online Travel Products

The two largest categories of online travel are airline ticket sales and hotel bookings. In 2010, airline ticket sales represented 53% of total online travel purchases, followed by hotel bookings at 27%.

Airline tickets are the most common travel product researched and purchased online, with global online sales reaching 38% of overall global airline ticket sales in 2010. Online airfare sales are projected to grow at a 10% CAGR from 2010 through 2012. There are hundreds of airlines in operation, and the large choice of flight combinations and pricing options, highly variable real-time pricing and the advent of e-ticketing make flights well suited to online research and purchasing. We believe that the combination of choice and variability leads to a lack of confidence among users in the accuracy and comprehensiveness of flight data. Users often search for flights multiple times and on multiple travel websites.

Hotel bookings are the fastest growing online travel category. Online hotel bookings are projected to grow at a 11% CAGR from 2010 through 2012. Additionally, only 23% of 2010 hotel bookings occurred online. The hotel market is a highly fragmented travel category, with hundreds of thousands of properties worldwide. This often leaves potential travelers with hundreds of properties to choose from in any given city. Given the significant differentiation among hotels, travelers will typically spend considerable time online researching a hotel stay, making hotel bookings highly suitable for the online channel. We believe that the number of consumer choices combined with the predominately fixed nature of hotel operating costs, results in a willingness of hoteliers to pay a premium for quality referrals.

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Online Travel Advertising: A Large Opportunity to Grow Share of Total Advertising Spend

Online advertising is a large and growing market. The combined online and offline advertising spend for all products and services in 2010 was $588 billion. Of this amount, $70 billion, or 12%, was spent online. Furthermore, for the period from 2010 through 2015, online advertising is projected to grow at a 15% CAGR, as compared to the 6% CAGR projected for combined online and offline advertising.

Travel represents one of the largest advertising categories, with advertisers spending $31 billion globally on travel-related advertising in 2010. Of this amount, only $4 billion, or 14%, was spent online with the remainder being spent primarily on traditional media, up from $1.4 billion, or 5% of total travel advertising spend in 2005. This represents a 26% CAGR in online travel advertising spend between 2005 and 2010. We believe that travel advertising will continue to move from offline to online as travel purchases continue to move online. Online travel advertising can also be a more efficient advertising channel, as it enables advertisers to directly target individuals who are researching and planning travel. The online travel advertising market is expected to reach $9 billion by 2015, a CAGR of 15% between 2010 and 2015.

Key Trends in Mobile Travel Planning

Mobile phone adoption across the world continues to grow at a rapid pace, creating a strong marketplace for mobile travel applications. The International Telecommunications Union estimated that there were 4 billion mobile subscribers in the world at the end of 2008, representing 61% of the world’s population. In addition, in March 2009 they projected this number to grow by at least 1 billion in the next few years. We expect that over time, an increasing number of people will use their mobile devices for travel research, planning and booking. Today, there are more than 2,000 travel-related applications available for the iPhone, Android and BlackBerry.

The opportunity for mobile advertising is large and growing. U.S. mobile advertising spend is expected to grow from $733 million in 2009 to $4.7 billion in 2014, a 45% CAGR. We believe the mobile medium provides a unique opportunity for advertisers to reach travelers with immediately actionable, personalized and context-relevant travel offers.

Challenges of Our Industry

Challenges for Consumers

The Internet has dramatically increased the amount of information readily available to travelers. Planning travel online should be a quick and easy process. However, prices and availability change frequently, and information is often fragmented across hundreds of travel sites. Traditional travel websites can be slow and confusing and often lack comprehensive search results. A 2010 survey by Forrester Research Inc. showed increasing dissatisfaction among users with the online booking experience. Only 47% of U.S. online leisure travelers surveyed said they enjoy using the internet to plan and buy travel, down from 53% in 2007. The same survey showed that only 37% of U.S. online leisure travelers believed that travel websites clearly present choices and tradeoffs, down from 39% in 2008. These limitations can make it frustrating for people to find, purchase and manage their travel online. As a result, we believe that travelers continue to search multiple sites for the best prices and options to meet their travel needs.

Challenges for Travel Suppliers and OTAs

Travel suppliers and OTAs face two main challenges. One is to distribute their travel products to as many travelers as possible, while still maintaining their brand and owning the customer relationship. In distributing their travel inventory through third party sites, they lose the opportunity to cross sell or upsell additional products and to build brand loyalty. The second challenge they face is to advertise their services to the right audience at the right time, in a cost effective manner. The majority of travel advertising dollars is currently spent in offline media channels, including TV, radio, print and outdoor campaigns. Offline travel advertising can be expensive,

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and its effectiveness can be difficult to measure and track. Online advertising offers many improvements to traditional advertising, but can still suffer from audience fragmentation, generic advertising placements and complex pricing schemes. Many online advertising platforms do not solve this combination of problems effectively.

Our Strengths

KAYAK Provides a Fast, Intuitive and Comprehensive Travel Planning Experience

KAYAK creates a better way to shop for travel online. We use proprietary software and algorithms to quickly find, consolidate and sort travel information from hundreds of websites. We present these results through an intuitive interface, providing a single place for our users to plan their travel. In 2011, 899 million user queries for travel information were processed through our websites and mobile applications. Once a KAYAK user finds what they want to buy, we give them the flexibility to purchase directly from travel suppliers or through OTAs, and in some cases, they can complete their bookings directly through our websites and mobile applications.

KAYAK is a Technology-Driven Company Focused on Rapid Innovation and the User Experience

We dedicate the majority of our attention to developing high performance technology. This technology powers our websites and mobile applications by rapidly searching through the large and complex range of travel industry data and presenting it in a clear and intuitive manner. Our proprietary technology detects and removes inaccurate prices or results in this data. Our ranking software algorithm also determines which results are likely to be the most relevant to the user. Our focus on technology is reflected in our employee base. The majority of our employees are either software engineers or technologists, and we believe we have one of the strongest technology teams in the travel industry. We strive to innovate faster than our competitors, and we release new code to our websites almost every week. Our mobile applications are examples of our development capabilities.

KAYAK’s Users are Loyal

We believe that our users are loyal to our brands, products and services. According to a June 2011 study conducted by TNS Custom Research, Inc. on our behalf, KAYAK is a leading brand among the major online travel sites in the U.S. for attributes such as “Finds all the best prices in one place” and “Smarter way to search for travel online.” In 2011, 78% of our query volume was generated from people who directly visited our websites, and only 5% of our query volume was generated by users referred to us from general search engines.

KAYAK’s Proprietary Distribution and Advertising Platform is Optimized for the Travel Industry

We provide travel suppliers and OTAs with access to a valuable audience of people searching for travel information. We also offer these travel companies multiple ways to reach this audience through both our query results and a variety of advertising placements.

On the distribution side, our query results include real-time pricing and availability information from travel suppliers, OTAs and technology providers. We query and display information in direct response to a KAYAK user’s query parameters. Our sorting and filtering tools allow users to narrow the query results to meet their specific travel plans. If a user then selects one of these results, we send them directly into the travel supplier’s or OTA’s purchase process or in many cases, users may complete hotel bookings directly through our websites or mobile applications.

On the advertising side, our innovative platform allows advertisers to target their placements, create advertising content and link the user to the relevant page on the advertiser’s website, all based on the user’s search parameters. As examples, an airline can limit its advertisements to appear only for the cities that it serves, or a

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hotelier can purchase advertisements only for dates where its occupancy rates are low. By dynamically creating the content of their advertisements based on these specific search parameters, the airline can include the cities the users searched in their advertisement and the hotelier can advertise a special rate to try to increase their occupancy. The same search parameters can be passed through to an advertiser after a potential traveler clicks on one of their advertisements. This lets the advertiser show the traveler products which meet his or her specific travel needs, without requiring the traveler to do additional work. We believe that our ability to pass a prospective traveler through to the relevant booking page increases the likelihood that a transaction will be completed.

KAYAK’s Unique Business Model is Highly Scalable

We designed our business model and technology platform to be highly scalable and cost efficient. Our software and systems have been designed from inception to handle significant growth in users and queries, without requiring significant re-engineering or major capital expenditures. In addition, we use a combination of our own proprietary software, public domain technologies and tiered pricing arrangements with third-party software providers so that as queries continue to grow, we do not incur proportionately higher software costs. Since all travel products are purchased by our users directly on the travel supplier’s or OTA’s website or through third-party booking and fulfillment providers, we do not incur meaningful costs or overhead associated with fulfillment or customer service for those travel products. We have relatively low fixed operating costs, and the largest component of our variable operating cost is discretionary marketing.

The KAYAK Team Has Deep Industry Experience and Focus

Cofounders of Expedia, Travelocity and Orbitz formed KAYAK in 2004. Our team has extensive and longstanding relationships across the travel industry and, unlike general search engine companies, we focus on a single market category—online travel. Our mission is to build the best assortment of tools and services to meet the needs of travelers. To accomplish our goal, we have assembled technology and business teams, which each include people that have worked together over many years. In addition to the strength of our management team, our investors include some of the most prominent venture capital and private equity firms, including Sequoia Capital, Accel Partners, General Catalyst Partners and Oak Investment Partners.

Our Growth Strategy

Continue to Improve and Expand Our Services

We are dedicated to offering people the best online travel planning experience. To provide the most comprehensive set of results, we maintain relationships with hundreds of travel suppliers and OTAs and regularly add new sources of travel information. We continue to develop better software and algorithms to reduce the time required to perform a query, enhance the relevance of the results and make the booking path easier for travelers. Additionally, we constantly review the feature set and design of our websites and mobile applications for areas of improvement, and we release new code to our websites on nearly a weekly basis. Examples of enhancements to our offering include the introduction of KAYAK on multiple mobile platforms, a trip management tool, KAYAK Explore, a map-based search feature and the ability for users to complete bookings directly through us.

Expand Our Booking Path Capabilities

We believe that many consumers would prefer to complete their bookings without having to leave our websites and mobile applications. In March 2011, we added the capability for consumers to make hotel reservations through our U.S. website. We have since introduced this feature to our mobile applications and across other geographies. Consumers benefit from a more seamless user experience, and we benefit from an increase in completed transactions. We intend to extend this capability to flights and rental cars.

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Increase Consumer Awareness of Our Brands

We believe there is significant opportunity to increase the number of people who use our websites and mobile applications. According to studies conducted by TNS Custom Research, Inc. on our behalf, as of October 2009, only 9% of online travelers in the U.S. included KAYAK in an unprompted list of online travel sites, known as “unaided awareness.” Since that time, we commenced a broad reach marketing program, which resulted in our unaided awareness increasing to 31% for the month of January 2012. By comparison, the four highest rated travel brands in this category had an average unaided awareness of 47%, according to this survey. We will continue to invest in broad reach marketing to increase our unaided awareness.

Grow Our Business Internationally

We operate websites in 14 countries outside of the U.S., including Germany, the United Kingdom, France, Spain, Italy and Austria. We believe that the international opportunity for our services is sizable, and we intend to continue to invest in both headcount and marketing in 2012. As part of this strategy, we acquired swoodoo, a leading German travel search company, in May 2010 and checkfelix.com, a leading Austrian travel search company, in April 2011. Furthermore, we established a team headquartered in Zurich, Switzerland to coordinate our European efforts.

Extend our Leadership Position in Mobile Applications

Mobile devices represent an important growth area in both audience and query volume. Smartphone adoption and usage are increasing quickly, and new touch screen devices like the Apple iPad provide opportunities for innovation in features and functionality. We have seen rapid adoption of our KAYAK mobile applications – with over 13 million downloads across several mobile platforms since the release of our first mobile application in March 2009. We believe that our leadership position in travel-related mobile applications, which we plan to extend through continued product development, will enhance the loyalty to our brand, products and services.

Our Brands – KAYAK, swoodoo, and checkfelix.com

We operate our websites and mobile applications under three brands: KAYAK, swoodoo and checkfelix.com. Each of these brands provides the same core set of free services including flight, hotel and other travel search, flight status updates, pricing alerts and itinerary management.

We use our KAYAK brand across multiple platforms including: KAYAK.com; local websites in 14 countries outside of the U.S.; a mobile website, m.KAYAK.com; and the KAYAK mobile smartphone applications currently available on the iPhone, iPad, Android, BlackBerry, Symbian and other platforms. KAYAK branded websites and mobile applications account for most of our query volume, and we will focus our future growth efforts on building the KAYAK brand in the U.S. and in key international markets and growing the swoodoo brand in Germany.

The SideStep brand, which we acquired in December 2007, was used for our sidestep.com website. In January 2011, we determined that we would not support two brand names and URLs in the United States and began redirecting traffic from sidestep.com to KAYAK.com. The swoodoo brand, which we acquired in May 2010, is used for our swoodoo.com website and the related mobile travel application, which is a leading travel search platform in Germany. We acquired JaBo Vertrieb-und Entwicklung GmbH, which supported the checkfelix.com brand, in April 2011. Checkfelix.com is a leading travel search platform in Austria.

Our Distribution and Advertising Platform

Our websites offer travel suppliers and OTAs an efficient and flexible platform to distribute their travel products through our query results and to advertise throughout our website. We also provide our services on a co-branded, revenue sharing basis through certain third party websites, such as Bing Travel. We are continuing the development of a distribution and advertising platform for our mobile applications.

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Distribution Revenues

We generate distribution revenues by sending qualified leads to travel suppliers and OTAs and by facilitating hotel bookings directly through our websites and mobile applications. After a user has entered a query on our website, reviewed the results, and decided what travel product they are interested in buying, we send the user directly into the travel supplier’s or OTA’s purchase process to complete the transaction, and in many cases, users may now complete hotel bookings directly through our websites and mobile applications. Travel suppliers and OTAs have the flexibility to pay us either when these qualified leads click on a query result or when they purchase a travel product on the travel supplier or OTA website. Booking and fulfillment providers pay us after a user completes a booking through the KAYAK websites or mobile applications. We separately negotiate and enter into our distribution agreements, and these agreements set forth the negotiated payment terms for the applicable travel supplier, OTA or booking and fulfillment providers. Travel suppliers and OTAs are generally able to select the payment terms in these agreements based on what best suit their needs.

Advertising Revenues

We have a proprietary advertising platform called the KAYAK Network, or KN. KN allows advertisers to target the placement and message of their advertisements to the search parameters entered by our users, such as the traveler’s origin, destination and desired travel dates. This technology allows advertisers to target their advertisements better, create more effective messages and to transfer users to their websites more efficiently. Our platform allows advertisers to limit placements to instances when the advertiser has an offer that is relevant to a user’s query. For example, an airline can ensure it only advertises when a user searches for a route offered by such airline, and a hotelier can ensure it only advertises to users who have searched for dates when the hotelier has low occupancy. We also enable advertisers to use a traveler’s search parameters to dynamically create targeted messages, and after the traveler clicks on an advertisement, we can pass the same search information through to the advertiser, thus increasing the likelihood of a purchase on their website.

Our platform gives advertisers flexibility in terms of placement types and payment structures. We offer a variety of advertising inventory including text-based sponsored links, graphical display advertisements, mobile advertisements and email-based placements. We also offer a variety of payment terms including cost per click, cost per impression, cost per acquisition or fixed fees.

Technology and Infrastructure

KAYAK is a technology-driven company. Our technology platform powers our websites and mobile applications by rapidly searching through the complex and fragmented range of travel industry data and presenting comprehensive and relevant travel query results to the user in a clear and intuitive manner.

Search Capabilities

Our software and systems have been designed from inception to handle significant growth in users and queries, without requiring significant re-engineering or major capital expenditures. In 2011, we received and processed 899 million user queries for travel information.

When a travel query is entered on one of our websites or mobile applications, our technology platform analyzes the travel parameters, determines which websites and other travel databases have relevant travel information and then queries those multiple sources in parallel. Many of those sources operate with differing protocols, and therefore return results in slightly different ways and in differing time frames. Our platform gathers, prioritizes and standardizes this travel data. Our proprietary software then detects and eliminates inaccurate prices or results in this data, and our ranking software then determines which results are likely to be the most relevant and useful to the user. Our technology platform completes these processes and returns a comprehensive and relevant set of results within moments of receiving the travel query from the user.

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Website Design and Hosting

Reliability, speed and integrity are important to us. We have designed our websites and mobile applications using a combination of our own proprietary software and a variety of open source or other public domain technologies. Where appropriate, we have chosen to use public domain technologies to develop and maintain our websites and mobile applications because we believe they are widely used and well proven by the engineering community and end-users, and, therefore, offer us a reliable and efficient development environment and infrastructure. Such technologies also enable us to provide our users with a stable web or mobile experience and are often free. Our limited and selective use of commercially available software means that as we continue to grow the number of users that visit our websites and download our mobile applications, we do not incur significant additional software costs or software licensing fees.

Our websites are hosted on hardware and software located at third-party facilities in Medford and Somerville, Massachusetts and Freiburg, Germany. We also use content delivery networks and third-party domain name system, or DNS, services to optimize routing and increase the speed of our website pages. We are committed to ensuring that our websites are highly available. Our use of multiple secured hosting facilities provides us with power redundancy and expandable and redundant bandwidth, and we believe these facilities are well suited to fit our current and planned business needs.

Mobile Applications and Platforms

We offer mobile applications for the iPhone, iPad, Android, BlackBerry, Symbian and other platforms. These applications combine the speed and comprehensiveness found in our website experience with the convenience and portability offered by today’s smartphones and tablets. To enhance the mobile experience, we have also implemented mobile-specific functionality in these applications, such as currency conversion, visual flight status, airport guides, offline travel itineraries and location-based features.

As some smartphone users prefer to use the web browser on their phones rather than download a separate application, we also offer a mobile-optimized website. These users are automatically redirected to m.KAYAK.com, where we provide an “application-like” experience, including a streamlined interface, touch screen functionality and assisted input based on the user’s location.

Focus on Innovation

We strive to continually improve the user-experience on our websites and mobile applications. For example, we routinely work to improve our software and algorithms to further reduce the time required to return query results. We review the feature sets and design of our websites and mobile applications on a regular basis to identify areas for improvement. To aid in our review, we conduct regular formal usability testing, focus groups and comparison testing of new features. We release new code to our websites on a nearly weekly basis. Some examples of our past innovations include a user interface capable of updating page elements without reloading the entire page and “sliding bars” and other tools to filter query results based on relevant criteria, such as specific departure and arrival times for flights.

Certain costs to develop internal use computer software are capitalized because these costs are expected to be recoverable, while costs incurred during the preliminary project stage, as well as maintenance and training costs, are expensed as incurred. We capitalized software and website development costs of $0.6 million, $1.4 million and $1.0 million during the years ended December 31, 2009, 2010 and 2011, respectively.

Avoid Unnecessary Complexity

As technology organizations grow, a common danger is that the software code grows in complexity and can become difficult to maintain. We have been cognizant of this industry tendency since we began operations, and accordingly have designed our software architecture to establish basic rules of separation, dependency and

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simplicity. For the same reasons, we are purposeful in our use of industry standard hardware and our maintenance of a low technology footprint in our data centers. This pragmatic, “Keep It Simple” culture continues to enable us to rapidly and reliably adapt our system to new products and capabilities.

Intellectual Property

Our intellectual property, including patents, trademarks, copyrights and trade secrets are an important component of our business. We also rely on confidentiality procedures and contractual provisions to protect our proprietary technology and our brands. In addition, we enter into confidentiality and invention assignment agreements with our employees and consultants and confidentiality agreements with other third parties.

Our registered trademarks include: KAYAK, KAYAK.com, KAYAK Network, Search One and Done, SideStep, checkfelix.com and swoodoo. All of these trademarks, other than swoodoo and checkfelix.com, are registered in the U.S. and many of them are also registered in other jurisdictions.

We have ten issued U.S. patents and eleven U.S. patent applications for various aspects of our technology. Our patents expire at various dates between March 2021 and October 2026.

Marketing

We believe that continued investment in marketing is important to attracting new users to our websites and mobile applications. We balance our marketing investments between brand marketing campaigns designed to grow brand awareness and online marketing investments designed to generate additional query volume.

Brand Marketing

To grow brand awareness, we advertise in broad reach media, including television, outdoor and online display media. During 2011, we spent $57.7 million on KAYAK, swoodoo and checkfelix brand marketing. We measure the return on investment of our brand marketing through online brand tracking studies and overall query growth. We view the costs of our offline brand marketing campaign as relatively fixed, and we believe that as our revenues grow these costs will decrease as a percentage of our total revenues.

Online Marketing

We also market our services and acquire traffic to our websites by purchasing travel-related keywords from general search engines and through other online marketing channels. The purchase of travel-related keywords consists of anticipating what words and terms consumers will use to search for travel on general search engines and then bidding on those words and terms in the applicable search engine’s auction system. As a result, we bid against other advertisers for preferred placement on the applicable general search engine’s results page. We spent $45.6 million on online marketing in 2011.

We plan to continue both broad reach advertising and online advertising for the foreseeable future.

Strategic Relationships

In an effort to continue to grow our business and offer exceptional services to our users, we enter into strategic relationships with travel suppliers, OTAs, general search engines and travel technology companies. Our strategic relationships include the following:

Orbitz Worldwide, Inc.

We have maintained a strategic relationship with Orbitz Worldwide, Inc. or Orbitz, since 2004. Under the terms of our current long-term agreement, which we entered into in April 2009 and have subsequently amended,

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Orbitz provides us with access to their travel information and pays us for any transactions we send to one of their websites. In return, we provide exclusivity to Orbitz relating to the display of certain core query results. This agreement expires December 31, 2013.

Google Inc.

We have maintained a strategic relationship with Google since 2004. Under the terms of our current long-term agreement, which we entered into in December 2004, and have subsequently amended, Google provides us with sponsored link advertisements that, in addition to our own advertisements, are placed throughout our websites at locations we determine. Google and KAYAK share the revenues that are generated from these advertisements. Our agreement with Google expires October 31, 2012.

ITA Software, Inc.

In March 2005 we entered into an agreement to license faring engine software from ITA. This faring engine software provides airfare content that is used in a majority of our domestic flight query results and to supplement our international flight query results. This agreement expires December 31, 2013.

Other Relationships

In addition, our 2011 commercial relationships have included agreements with over 300 travel suppliers, OTAs and technology providers. These relationships provide us with access to travel information, booking, fulfillment and customer service solutions as well as distribution and advertising revenue, and are established and managed by our Business Development, Advertising Sales and Account Management teams. Our Business Development team negotiates agreements with travel suppliers, OTAs and technology providers for access to their travel content, for payment from distribution-related referrals and for content delivery, booking, fulfillment and customer service solutions. This team is focused on contract negotiation and relationship management. Our Advertising Sales team calls on travel suppliers, OTAs and their advertising agencies and negotiates advertising insertion orders for placements throughout our websites and mobile applications. Our Account Management team works with travel suppliers and OTAs to implement advertising campaigns and optimize spend.

These other significant relationships include:

OTAs: Airfare.com, airline-direct.de, Expedia (including Hotwire, Hotels.com and CarRentals.com), Fareportal, Getaroom, Priceline.com (including Booking.com), ODIGEO (including Opodo and eDreams), Travelocity, Travel Holdings (including Easy Click Travel and Tourico Holidays) and Travix (which manages a portfolio of travel-focused websites, including Vayama and EasyToBook.com);

Airlines: Air Canada, airberlin, AirTran Airways, Alaska Airlines, American Airlines, BravoFly, British Airways, Delta Air Lines, easyJet Airline, JetBlue Airways, Lufthansa Airlines, United Air Lines, Virgin America and Virgin Atlantic;

Hotels: Best Western, Choice Hotels, Harrah’s Entertainment, Hyatt Hotels and Resorts, InterContinental Hotels Group, La Quinta Inn & Suites, Marriott, Starwood Hotels and Wyndham;

Rental Cars: Alamo Rent A Car, Auto Europe, Avis Budget Group, Dollar Thrifty Automotive Group, Enterprise Rent-A-Car, Hertz Rent-a-Car and National Car Rental;

Technology Providers: Amadeus, DoubleClick, IAN, Pegasus, SynXis, TravelClick, TRX and World Choice Travel.

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Competition

We operate in the highly competitive online travel category. We compete both to attract users to our websites and mobile applications and to attract travel suppliers and OTAs to participate in our query results and purchase advertising placements on our websites.

Competition for Users

In our efforts to attract and retain users, we compete with travel suppliers, OTAs, search engines and other travel information and research websites. Our major competitors include general search engines such as Google and Bing, OTAs such as Expedia and Orbitz and other travel information sites such as TripAdvisor and Travelzoo. In addition, airlines, hotels and other travel suppliers are increasingly focused on attracting users directly to their own websites.

Competition for Advertisers

While we compete with travel suppliers and OTAs to bring users directly to our websites, such parties also advertise on our websites and mobile applications. We believe that travel suppliers will spend their advertising dollars on the websites and offline media that results in the highest return on investment. This means that we directly compete with search engines, OTAs and traditional offline advertising sources such as TV and print media for travel supplier advertising dollars. We also compete with search engines and offline media sources for advertising from OTAs that look to market their services to travelers. We believe that travel suppliers and OTAs will direct their advertising dollars to the websites, mobile applications and offline media sources that offer the highest return on investment.

Employees

As of March 31, 2012, we had 169 employees, consisting of 141 in the U.S., 15 in Zurich, 7 in Germany and 6 in England. Of those employees, 102 are on our engineering and development team. As of March 31, 2012, we also had an arrangement with an outsourced engineering team in Lithuania that provides us with approximately 21 contractors for engineering and development functions, a team of 27 contractors in Pakistan who provide engineering, data analysis and data operator functions, and one contractor in the U.S. that assists with engineering activities.

We consider our relationship with our employees to be good. None of our employees is covered by a collective bargaining agreement.

Government Regulation

Laws and regulations applying to businesses generally and to businesses operating on the Internet affect us. As the growth in Internet commerce continues, the number of laws and regulations specific to operating on the Internet is increasing and includes areas such as privacy, content, advertising, and information security. Moreover, the applicability to the Internet of existing laws governing issues such as intellectual property ownership and infringement, obscenity, libel and personal privacy is uncertain and evolving.

Air Transportation Advertising

Our travel suppliers and advertisers are subject to laws and regulations relating to the sale of travel, including regulations and standards promulgated by the Department of Transportation, or DOT, related to the advertising and sale of air transportation. We do not sell or book air transportation, and, therefore, we are not positioned similarly to the entities (such as air carriers and ticket agents) that are usually understood to fall within the scope of the DOT’s regulations and standards. Nevertheless, we intend to ensure that any content created by KAYAK is consistent with the DOT’s regulations and standards, and we seek representations of compliance from our travel suppliers and

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advertisers for content provided to or promoted by KAYAK. To the extent we expand our business model in the air transportation area, we could be subject to DOT oversight.

Legal Proceedings

In April 2009, Parallel Networks, LLC filed a complaint against us for patent infringement in the U.S. District Court for the Eastern District of Texas. The complaint alleged, among other things, that our website technology infringes a patent owned by Parallel Networks purporting to cover a “Method And Apparatus For Client-Server Communication Using a Limited Capability Client Over A Low-Speed Communications Link” (U.S. Patent No. 6,446,111 B1) and sought injunctive relief, monetary damages, costs and attorneys fees. The complaint was dismissed without prejudice in February 2010, but the plaintiff filed a new complaint against us on March 29, 2010 containing similar allegations. The case was set for trial on September 10, 2012. The court has since stayed proceedings in the district court pending resolution of plaintiff’s appeal of certain rulings by the court, which granted summary judgment on several claims in favor of us and other defendants.

In August 2010, Orbitz initiated arbitration with us through the American Arbitration Association in the state of New York. Orbitz contends that we violated the parties’ 2009 Promotion Agreement by failing to abide by certain exclusivity provisions relating to the display of certain advertising placements on our websites. It also contends that we owe it in excess of $2.5 million as a result of “net revenue” overpayments that Orbitz allegedly made to us over the past few years when Orbitz calculated and reported its own net revenue obligations under the agreement. We denied Orbitz’s allegations and asserted a number of affirmative defenses in response to both claims. A three-day evidentiary hearing took place in New York on May 24, 2011. On December 31, 2011, the arbitration panel issued an interim order that, with limited exceptions, found in our favor regarding the exclusivity provisions of the agreement. On the “net revenue claim,” the arbitration panel ordered the parties to engage in an audit. The audit firm provided its report in March 2012, which included 4 possible scenarios, all of which found that Orbitz underpaid KAYAK for 2008 and 2009 in varying amounts, between $49,047 and $2.85 million. The parties are currently briefing the net revenue issues, and will engage in limited discovery on damages followed by additional briefing thereafter. We expect a final decision by the arbitration panel after the briefing and discovery is completed.

On March 22, 2011, Orbitz filed a lawsuit against us in the Circuit Court of Cook County in Chicago, Illinois alleging that we violated the 2009 Promotion Agreement by failing to abide by certain exclusivity provisions because of our use of certain third party technology providers in connection with our hotel booking functionality. Orbitz sought a temporary restraining order to restrain our use of this booking feature. On March 25, 2011, the judge denied Orbitz’s request for a temporary restraining order, finding that Orbitz did not sustain its burden of showing a likelihood of success on the merits. On May 9, 2011, Orbitz initiated an arbitration asserting these same claims. On May 11, 2011, Orbitz voluntarily dismissed the court case in favor of continuing to arbitrate the matter. The parties are now in the process of finalizing the designation of the arbitration panel. No other deadlines have been set. We intend to vigorously defend ourselves in this matter.

On June 13, 2011, Source Search Technologies LLC filed a complaint against us for patent infringement in the U.S. District Court of New Jersey. The complaint alleges, among other things, that our website infringes a patent owned by Source Search entitled, a “Computerized Quotation System and Method.” According to the complaint, the patent allegedly allows a central computer to filter requests for quotes, and to interface to various vendor computers to obtain and forward these quotes to potential buyers of goods and services. We were served with the complaint on June 17, 2011. We filed a response on August 5, 2011, denying the allegations of patent infringement and asserting a counterclaim for declaratory judgment of non-infringement and invalidity. On November 3, 2011, the court terminated the case, pending the conclusion of the U.S. Patent Office’s reexamination of Source Search’s patent.

On September 15, 2011, LVL Patent Group, LLC (now known as CyberFone Systems, LLC, or CyberFone) filed a complaint against us for patent infringement in the U.S. District Court for the District of Delaware. The

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complaint alleges, among other things, that our technology infringes a patent owned by CyberFone purporting to cover a “Telephone/Transaction Entry Device and System for Entering Transaction Data in Databases” and seeks injunctive relief, monetary damages, costs and attorneys fees. More specifically, the complaint alleges infringement by providers who make, use, sell, offer to sell, or import a method of obtaining data transaction information entered on a telephone, forming a plurality of exploded data transactions for the single transaction, and sending different exploded data transactions to different destinations, using its mobile services network platform. We subsequently filed two motions to dismiss with the court and anticipate a ruling on these motions in mid-2012. We intend to vigorously defend ourselves in this matter.

In addition, from time to time, we may become involved in legal proceedings arising in the ordinary course of our business. Such proceedings, even if not meritorious, could result in the expenditure of significant financial and managerial resources.

Facilities

We lease approximately 7,375 square feet in Norwalk, Connecticut for our corporate headquarters. We maintain an office of approximately 29,381 square feet in Concord, which is used primarily by our technology team. In addition, we lease office space for our foreign subsidiaries in London, England, Munich, Germany and Zurich, Switzerland. Our leases are set to expire at varying dates between May 2013 and August 2017.

We believe our space is adequate for our current needs and that suitable additional space will be available to accommodate the foreseeable expansion of our operations.

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MANAGEMENT

Directors and Executive Officers

Below is a list of our executive officers and directors and their respective ages and positions as of April 11, 2012 and a brief account of their business experience.

Name	Age		Position
Daniel Stephen Hafner		43	Chief Executive Officer, Cofounder and Director
Paul M. English		48	Chief Technology Officer, Cofounder and Director
Melissa H. Reiter		43	Chief Financial Officer
Robert M. Birge		42	Chief Marketing Officer
Karen Ruzic Klein		42	General Counsel and Corporate Secretary
Keith D. Melnick		42	Chief Commercial Officer
Paul D. Schwenk		45	Senior Vice President of Engineering
William T. O’Donnell, Jr.		45	Chief Architect
Dr. Giorgos Zacharia		38	Chief Scientist
Dr. Christian W. Saller		40	Managing Director for Europe
Terrell B. Jones (1)		63	Director
Joel E. Cutler		54	Director
Michael Moritz		57	Director
Hendrik W. Nelis		48	Director
Brian H. Sharples		51	Director
Gregory S. Stanger		47	Director

(1) Chairman of our board of directors.

Executive Officers

Daniel Stephen Hafner, 43, is our cofounder and has been our Chief Executive Officer and a member of our board of directors since January 2004. Prior to founding our company, Mr. Hafner helped establish Orbitz, Inc., an online travel company, and served as Orbitz, Inc.’s Executive Vice President for Consumer Travel Services from May 2000 until December 2003. From June 1997 until April 2000, Mr. Hafner worked as a consultant with the Boston Consulting Group, a management consulting firm, and advised clients in the e-commerce, health care and industrial goods sectors. Mr. Hafner received a B.A. in economics from Dartmouth College and an M.B.A. from the Kellogg School at Northwestern University. The specific experience, qualifications, attributes and skills that Mr. Hafner brings to our board of directors are significant historical knowledge of KAYAK and relationships in marketing, business development and advertising.

Paul M. English, 48, is our cofounder and has been our Chief Technology Officer and a member of our board of directors since January 2004. Mr. English was previously Vice President of Technology for Intuit Inc. from March 1999 until March 2002. In 1997, he cofounded Boston Light Software Corp., which was acquired by Intuit Inc. in August 1999. He also helped establish Intermute Inc., a provider of anti-spam and anti-spyware solutions in May 2000. Mr. English also served as Senior Vice President of Product Management and Marketing and Senior Vice President Engineering at Interleaf Inc., a developer and marketer of software products and services, from February 1989 until December 1995. Mr. English has served on the board of directors of Partners-In-Health since October 2010 and Village Health Works since January 2010, two non-profit

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corporations aimed at providing health care to the poor. He received his B.A. and M.S. in computer science from the University of Massachusetts in Boston. As the cofounder responsible for much of the technology involved in our business, the specific experience, qualifications, attributes and skills that Mr. English brings to our board of directors are significant technical knowledge and insight on product strategy and a deep commitment to customer service.

Melissa H. Reiter, 43, was appointed our Chief Financial Officer in March 2012. Prior to that she served as our Senior Vice President of Finance and Investor Relations since October 2009. From October 2006 until October 2009, Ms. Reiter held various positions, most recently as the Vice President of Finance, for Potbelly Sandwich Works, LLC, a restaurant chain. From May 2002 until January 2006, she held various positions, most recently as Controller, at Orbitz, Inc. and prior to that, from August 1991 until May 2002, she held various positions, most recently as senior manager, at Arthur Andersen LLP. Ms. Reiter received a B.S. in business administration from Miami University, Ohio.

Robert M. Birge, 42, has been our Chief Marketing Officer since May 2009. Mr. Birge has more than 15 years of experience in marketing, most recently as the Chief Marketing Officer for IMG Worldwide, Inc., a sports, entertainment and media company, from August 2006 until May 2009. From April 2001 until July 2006, he held various management positions, including Managing Director, at TBWA/Chiat/Day, an advertising agency. From 1998 to 2001, Mr. Birge worked as a consultant with the Boston Consulting Group, where he assisted in the start-up phase of Orbitz, Inc. He received a B.A. in history and government from Dartmouth College and an M.B.A. from the Kellogg School at Northwestern University.

Karen Ruzic Klein, 42, has served as our General Counsel since November 2007 and our Corporate Secretary since February 2008. Prior to joining us, Ms. Klein served as Group Vice President, Legal, with Orbitz Worldwide, Inc., an online travel company, from November 2004 until October 2007. From July 2001 until November 2004, she served as Senior Counsel to Orbitz, Inc., and prior to that, she held various legal positions in technology and software companies, having started as an associate at Katten Muchin Rosenman LLP in 1995. Ms. Klein received a B.A. in political science and international relations from the University of Wisconsin and a J.D. from Chicago-Kent College of Law.

Keith D. Melnick, 42, has served as our Chief Commercial Officer since August 2010, prior to which he was the Executive Vice President of Corporate Development from June 2006 until August 2010 and Vice President of Business Development from February 2004 until June 2006. Prior to joining us, Mr. Melnick was a management consultant with the Boston Consulting Group since May 1999, where he concentrated primarily on travel, e-commerce, financial services and industrial goods and helped found Orbitz, Inc. From 1996 until 1999, he served in Revenue Management and Finance with American Airlines, Inc. Mr. Melnick received a B.S. in mechanical engineering from the University of Illinois and an M.B.A. in finance with highest honors from the University of Southern California.

Paul D. Schwenk, 45, has been our Senior Vice President of Engineering since February 2004 and is responsible for our product development. From 1999 until 2004, Mr. Schwenk was a Senior Group Manager at Intuit Inc., a maker of financial and tax preparation software. From 1998 until 1999, he worked as a Senior Software Engineer at Boston Light Software Corp., a developer of web products and software. In 1997, Mr. Schwenk cofounded, and was the President of, Digital Direct Network, a multi-media networking company. Prior to that, he worked as a software engineer for each of NetCentric Corporation from 1995 until 1997, Avid Technology Inc. from 1994 until 1995 and Interleaf Inc. from 1990 until 1994. Mr. Schwenk received a B.S. in computer science from Rochester Institute of Technology.

William T. O’Donnell, Jr., 45, has been our Chief Architect since February 2004 and is responsible for our mobile products and strategy. From 2003 to 2004, he served as Chief Architect at Inuit, Inc. From 1999 to 2003 he served as staff software engineer at Inuit, Inc. From 1998 to 1999 he served as Chief Architect at Boston Light Software. From

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1997 to 1998 he served as Chief Technology Officer at Digital Direct Network. From 1995 to 1997, he served as software engineer at Interleaf, Inc., and from 1989 to 1995 he served as software engineer at a variety of technology companies. Mr. O’Donnell received a B.S. in computer engineering from Carnegie Mellon University.

Dr. Giorgos Zacharia, 38, has been our Chief Scientist since February 2009. In February 2007, he founded Emporics Capital Management, a hedge fund management firm, of which he is a general partner. In January 1999, Dr. Zacharia founded Open Ratings Inc., a provider of supply risk management services which was acquired by Dun & Bradstreet Corp. in 2006, and served as its Chief Technology Officer and Chief Scientist until July 2008. Dr. Zacharia has won five medals in International Mathematical and Physics Olympiads and received an M.S. and a Ph.D. in computer science from the Massachusetts Institute of Technology, where he studied as a Fulbright scholar and a Telecom Italia fellow. Dr. Zacharia holds three algorithm patents.

Dr. Christian W. Saller, 40, has been our Managing Director for Europe since October 2010 and was our Managing Director for Germany from May 2010. Since February 2008, he has also served as the Chief Executive Officer of swoodoo AG, a German travel search engine that we acquired in May 2010. Dr. Saller previously was the Chief Financial Officer of GIGA Television GmbH, a gaming television network in Germany, from April 2006 until January 2008. From September 2005 until March 2006, Dr. Saller served as the Chief Operating Officer of Betty TV AG, an interactive TV infrastructure company. He received a Ph.D. in mathematics from Munich Technical University and an M.B.A. from the London Business School.

Directors

The following information pertains to our directors, their ages, principal occupations and other directorships for at least the last five years and information regarding their specific experience, qualifications, attributes or skills. In selecting directors, we consider factors that are in our best interests and those of our stockholders, including diversity of backgrounds, experience and competencies that our board of directors desires to have represented. These competencies include: independence; adherence to ethical standards; the ability to exercise business judgment; substantial business or professional experience and the ability to offer our management meaningful advice and guidance based on that experience; ability to devote sufficient time and effort to the duties of a director; and any other criteria established by our board of directors together with any core competencies or technical expertise necessary for our committees. We believe that each director possesses these qualities and has demonstrated business acumen and an ability to exercise sound judgment, as well as a commitment of service to us and to our board of directors.

Terrell B. Jones, 63, has been the Chairman of our board of directors since March 2004 and also serves as the Chairman of our nominating and governance committee and as a member of our audit committee. Mr. Jones has been the President of Essential Ideas, a travel and e-commerce consulting firm, since he founded it in May 2002. Prior to founding Essential Ideas, Mr. Jones served in various positions with The SABRE Group, a distributor of electronic travel-related products and services, from 1986 until 2002, including most recently as President and Chief Executive Officer of Travelocity.com Inc., an online travel services provider which he helped found and which is currently a subsidiary of The SABRE Group, from 1996 until 2002 and Chief Information Officer of The SABRE Group from 1996 until 1998. He has served on the board of directors and audit committee of Earthlink, Inc., a publicly-traded Internet service provider, since May 2003. Additionally, he is member of the board of directors of Rearden Commerce Inc., a privately held provider of web-based services ranging from travel and entertainment to shipping and event planning, since June 2006, Smart Destinations, a privately held provider of pre-paid access to sightseeing destinations, since July 2009 and Luxury Link, LLC, an online luxury travel information provider since July 2011. Mr. Jones previously served on the board of directors and audit committee of Earthlink, Inc., a publicly-traded Internet service provider, from May 2003 until March 2011. He has also previously served on the board of directors and audit committee of Overture Services, Inc. from January 2002 until June 2003, La Quinta Corp. from May 2004 until June 2006, the board of directors of Travelocity.com Inc. from March 2000 until May 2002 and the board of directors of Entrust, Inc. from November 1998 until 2004, where he also served on the compensation committee. He received a B.A. in history from

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Denison University. The specific experience, qualifications attributes and skills that Mr. Jones brings to our board of directors are approximately 29 years of experience in the travel industry, a knowledge of the interaction between e-commerce and travel sectors and public company audit and board experience.

Joel E. Cutler, 54, has served as a member of our board of directors since March 2004 and also serves on our compensation committee. Mr. Cutler is a managing director of General Catalyst Partners, a venture capital firm that invests in technology companies, which he cofounded in 2000. Prior to cofounding General Catalyst Partners, he cofounded and operated numerous businesses in the travel, information services, specialty retail, consumer direct marketing and payment processing industries. These businesses include: National Leisure Group, a leisure travel technology and distribution company; Retail Growth ATM Systems, a national ATM and interactive network provider; and Starboard Cruise Services, an operator of duty-free retail stores, for whom he served as Chairman of the board of directors and Chief Executive Officer from 1998 until 2002. Mr. Cutler has served on the board of directors and the audit and compensation committees of FanSnap, Inc., an online ticket comparison shopping site, since October 2007, and Roost, Inc., a real estate search engine operator, since March 2005, all of which are privately held companies. He has also served on the board of directors of TravelPost, Inc., a privately held online hotel reviews and ratings source operator, since March 2010. He previously served on the board of directors of ITA Software, Inc., a provider of airfare pricing and shopping, OLX Inc., an operator of a website for classified ads, from September 2006 until August 2010, and Reveal Imaging Technologies, Inc., a developer of threat detection software and services, from July 2003 until August 2010, all of which were privately held companies during the periods of his service. He served on the compensation committee of OLX Inc. and Reveal Imaging Technologies, Inc. Additionally, he is a member of the board of directors of Beth Israel Deaconess Medical Center, Children’s Hospital Boston and The Crohn’s and Colitis Foundation of America. Mr. Cutler received a B.A. in government and economics from Colby College and a J.D. from Boston College Law School. The specific experience, qualifications, attributes and skills that Mr. Cutler brings to our board of directors are strong financial acumen and a unique perspectives from providing guidance and counsel to a wide variety of companies in the online technology sector.

Michael Moritz, 57, has served as a member of our board of directors since December 2007 and also serves on our nominating and governance committee. Mr. Moritz has been a member of Sequoia Capital, a venture capital fund, since 1986. Prior to joining Sequoia Capital in 1986, he worked in a variety of positions at Time Warner and was a Founder of Technologic Partners, a technology newsletter and conference company. Mr. Moritz has been a member of the board of directors of Green Dot Corporation, a publicly-traded financial services company, since February 2003, where he serves on the compensation committee and nominating and corporate governance committee, and of LinkedIn Corporation, a publicly-traded online professional network, since January 2011. He has previously served on the boards of directors of Flextronics Ltd., Google Inc., PayPal, Inc., Yahoo! Inc. and Zappos.com, Inc. He received an M.B.A. from The Wharton School, University of Pennsylvania and an M.A. from the University of Oxford. The specific experience, qualifications attributes and skills that Mr. Moritz brings to our board of directors are his 25 years of experience in the venture capital industry and his service on the boards of directors of a range of private and publicly-traded companies.

Hendrik W. Nelis, 48, has served as a member of our board of directors since May 2006 and also serves as the Chairman of our compensation committee and as a member of our audit committee. Mr. Nelis is a partner at Accel Partners in London, a venture capital fund which he joined in July 2004. Prior to joining Accel Partners, Mr. Nelis was an investor at Perry Capital from 2002 until 2004, a large hedge fund, where he invested in public communications, media and technology companies. From 1999 until 2002, he was an investment banker at Goldman Sachs International, where he advised businesses on corporate finance and mergers and acquisition transactions. Prior to joining Goldman Sachs, Mr. Nelis founded E-Motion, a venture-backed software company. From 1989 to 1993, Mr. Nelis was at Hewlett-Packard in Palo Alto where he held various engineering positions. He received an M.B.A. with distinction from Harvard Business School and a Ph.D. and M.S. in electrical engineering from Delft University of Technology in The Netherlands. The specific experience, qualifications attributes and skills that Mr. Nelis brings to our board of directors are a unique blend of technical expertise and international experience in investing in and advising media and technology companies.

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Brian H. Sharples, 51, has served as a member of our board of directors since December 2011. Mr. Sharples is one of the co-founders of HomeAway, Inc. and has served as its President, Chief Executive Officer and as a member of its board of directors since its inception in April 2004. Prior to that, Mr. Sharples was an angel investor from 2001 until 2004 and also served as Chief Executive Officer of Elysium Partners, Inc., a company in the vacation club ownership market, from 2002 until 2003. Mr. Sharples served as President and Chief Executive Officer of IntelliQuest Information Group, Inc., a supplier of marketing data and research to Fortune 500 technology companies, from 1996 to 2001, as President from 1991 to 1996, and as Senior Vice President from 1989 to 1991. Prior to IntelliQuest, Mr. Sharples was Chief Executive Officer of Practical Productions, Inc., an event-based automotive distribution business, from 1988 to 1989 and a consultant with Bain & Co. from 1986 to 1988. Mr. Sharples has served on the board of directors and compensation committee of Whaleshark Media, Inc., an online coupon site aggregator, since June 2011. He received a B.S. in math and economics from Colby College and an M.B.A. from the Stanford University Graduate School of Business. The specific experience, qualifications, attributes and skills that Mr. Sharples brings to our board of directors are his previous tenures in executive positions at various public and private technology companies and his experience in the vacation rental industry.

Gregory S. Stanger, 47, has served as a member of our board of directors since March 2011 and also serves as the Chairman of our audit committee and as a member of our compensation committee and our nominating and governance committee. Mr. Stanger serves as the Chief Financial Officer of oDesk Corporation, an online employment platform operator, and has so served since March 2012. Prior to that, he served as the Chief Financial Officer of Chegg, Inc., a textbook rental service, from March 2010 to October 2011. From June 2005 to June 2009, Mr. Stanger served as a venture partner at Technology Crossover Ventures, a private equity and venture capital firm, and was an executive in residence from December 2003 to June 2005. Prior to that, Mr. Stanger served as Senior Vice President, Chief Financial Officer and director of Expedia, Inc., an online travel company, from February 2002 to December 2003 and as its Chief Financial Officer from October 1999 to December 2003. Before joining Expedia, he served as Senior Director, Corporate Development of Microsoft Corporation and held various positions within Microsoft’s finance and corporate development departments since 1991. Mr. Stanger has previously served on the boards of directors of Netflix, Inc., drugstore.com, Inc. and numerous private companies. He served as audit committee chair on most of these boards, including Netflix and drugstore.com. Additionally, he has served on the board of the Yosemite Conservancy since 2010. He received a B.A. from Williams College and an M.B.A. from the University of California at Berkeley. Mr. Stanger brings to our board of directors significant financial and accounting experience from his service as the former chief financial officer of a publicly-traded corporation and the chief financial officer of Chegg, Inc. His managerial experience and his prior service on numerous boards make him a valuable source of strategic, operational, and corporate governance guidance.

Structure of the Board of Directors

Board Composition

Our business and affairs are managed under the direction of our board of directors. Upon completion of this offering, our board of directors will consist of eight members. Effective upon the completion of this offering, our amended and restated by-laws will provide that our board of directors will be fixed from time to time by resolution adopted by the affirmative vote of a majority of the total directors then in office. Each director’s term is subject to the election and qualification of his successor, or his earlier death, resignation or removal. Between annual meetings or special meetings of stockholders, any board vacancies may be filled by a vote of the majority of the remaining directors in officer.

Board Composition Prior to Completion of this Offering

The following describes the composition of our board of directors and related provisions of our current certificate of incorporation and various agreements. These arrangements will terminate upon completion of this offering.

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Our current amended and restated certificate of incorporation has provided, among other things, the holders of Series A convertible preferred stock the right to designate two members to our board of directors, the holders of Series C convertible preferred stock and holders of Series D convertible preferred stock the right to designate one member each to the board of directors and the holders of Series A convertible preferred stock, Series C convertible preferred stock and Series D convertible preferred stock, voting together an on as converted basis, the right to designate one member to the board of directors. In furtherance of those provisions, under our Stockholders’ Agreement and our Sixth Amended and Restated Stock Restriction and Co-Sale Agreement, two directors are to be designated by holders of more than 70% in the aggregate of Series A and Series A-1 convertible preferred stock, or the Series A designator, one director is to be designated by each of the holders of a majority of Series C convertible preferred Stock, or the Series C designator, and funds affiliated with Sequoia Capital, as holders of Series D convertible preferred stock, or the Series D designator, and two additional directors are to be designated jointly by the Series A designator, the Series C designator and the Series D designator. Additionally, the Series A designator has the right to designate two members of the compensation committee pursuant to our Seventh Amended and Restated Investor Rights Agreement. Currently, funds affiliated with General Catalyst Partners are the Series A designator, funds affiliated with Accel Partners are the Series C designator and funds affiliated with Sequoia Capital are the Series D designator. Pursuant to these arrangements, Messrs. Cutler and Jones are the appointees of the Series A designator, Mr. Nelis is the appointee of the Series C designator, Mr. Moritz is the appointee of the Series D designator and Mr. Stanger and Mr. Sharples are the joint appointees of the three designators.

Corporate Governance and Director Independence

Under Rule 5605(b)(1) of the NASDAQ Marketplace Rules, independent directors must comprise a majority of a listed company’s board of directors within one year of listing. In addition, the NASDAQ Marketplace Rules require that, subject to specified exceptions, each member of a listed company’s audit, compensation and nominating and governance committees be independent within one year of the date of listing. Audit committee members must also satisfy the independence criteria set forth in Rule 10A-3 under the Exchange Act. Under NASDAQ Marketplace Rule 5605(a)(2), a director will only qualify as an “independent director” if, in the opinion of that company’s board of directors, that person does not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. In order to be considered to be independent for purposes of Rule 10A-3, a member of an audit committee of a listed company may not, other than in his or her capacity as a member of the audit committee, the board of directors, or any other board committee: (1) accept, directly or indirectly, any consulting, advisory, or other compensatory fee from the listed company or any of its subsidiaries; or (2) be an affiliated person of the listed company or any of its subsidiaries.

Our board of directors has determined that Messrs. Cutler, Jones, Moritz, Nelis, Stanger and Sharples each qualify as an independent director under the corporate governance rules of the NASDAQ Stock Market. In making this determination, our board of directors affirmatively determined that none of Messrs. Cutler, Jones, Moritz, Nelis and Stanger have a relationship with us that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. Our board of directors has also determined that Messrs. Hafner and English are not independent under the NASDAQ Marketplace Rules because they are executive officers of KAYAK.

Board Committees

Our board of directors has established an audit committee, a compensation committee and a nominating and governance committee. The composition and responsibilities of each committee are described below. Members will serve on these committees until their resignation or until otherwise determined by our board of directors.

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Audit Committee

Our audit committee currently consists of Messrs. Jones, Nelis and Stanger, with Mr. Stanger serving as Chairman. Our audit committee has responsibility for, among other things:

• selecting and hiring our independent registered certified public accounting firm and approving the audit and nonaudit services to be performed by our independent registered certified public accounting firm;

• evaluating the qualifications, performance and independence of our independent registered certified public accounting firm;

• monitoring the integrity of our financial statements and our compliance with legal and regulatory requirements as they relate to financial statements or accounting matters;

• reviewing the adequacy and effectiveness of our internal control policies and procedures;

• discussing the scope and results of the audit with the independent registered certified public accounting firm and reviewing with management and the independent registered certified public accounting firm our interim and year-end operating results; and

• preparing the audit committee report required by the SEC to be included in our annual proxy statement.

Our board of directors has affirmatively determined that each of Messrs. Jones, Nelis and Stanger meets the definition of “independent director” for purposes of serving on an audit committee under Rule 10A-3 of the Exchange Act and the NASDAQ Marketplace Rules. We believe that each member of our audit committee meets the requirements for financial literacy. In addition, Mr. Stanger qualifies as our “audit committee financial expert.”

Our board of directors has adopted a written charter for our audit committee, which will be available on our website at KAYAK.com, the contents of which are not incorporated herein.

Compensation Committee

Our compensation committee currently consists of Messrs. Cutler, Nelis, and Stanger, with Mr. Nelis serving as Chairman. The compensation committee is responsible for, among other things:

• reviewing and approving compensation of our executive officers including annual base salary, annual incentive bonuses, specific goals, equity compensation, employment agreements, severance and change-in-control arrangements and any other benefits, compensation or arrangements;

• reviewing succession planning for our executive officers;

• reviewing and recommending compensation goals, bonus and stock compensation criteria for our employees;

• determining the compensation of our directors;

• reviewing and discussing annually with management our “Executive Compensation—Compensation Discussion and Analysis” disclosure required by SEC rules;

• preparing the compensation committee report required by the SEC to be included in our annual proxy statement; and

• administering, reviewing and making recommendations with respect to our equity compensation plans.

Our board of directors has affirmatively determined that each of Messrs. Cutler, Nelis and Stanger meets the definition of “independent director” for purposes of serving on a compensation committee under the applicable rules and regulations of the SEC and the NASDAQ Stock Market.

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Our board of directors has adopted a written charter for our compensation committee, which will be available on our website at KAYAK.com, the contents of which are not incorporated herein.

Nominating and Governance Committee

Our nominating and governance committee consists of Messrs. Jones, Moritz and Stanger, with Mr. Jones serving as Chairman.

The nominating and governance committee is responsible for, among other things:

• assisting our board of directors in identifying prospective director nominees and recommending nominees for each annual meeting of stockholders to our board of directors;

• reviewing developments in corporate governance practices and developing and recommending governance principles applicable to our board of directors;

• overseeing the evaluation of our board of directors; and

• recommending members for each committee of our board of directors.

Our board of directors has affirmatively determined that each of Messrs. Jones, Moritz and Stanger meets the definition of “independent director” for purposes of serving on a corporate governance and nominating committee under the applicable rules and regulations of the SEC and the NASDAQ Stock Market.

Our board of directors has adopted a written charter for our nominating and governance committee, which will be available on our website at KAYAK.com, the contents of which are not incorporated herein.

Compensation Committee Interlocks and Insider Participation

During the last fiscal year, Messrs. Cutler, Nelis and Mr. Gregory E. Slyngstad, one of our directors at the time, served on our compensation committee. Each of Messrs. Cutler, Nelis and Slyngstad all have relationships with us that require disclosure under Item 404 of Regulation S-K. These relationships consist of the following:

Sale of Travelpost.com

On March 5, 2010, we sold certain of our assets related to the website travelpost.com and its travel information business to The New Travelco, Inc., a Delaware corporation, which subsequently changed its name to TravelPost, Inc., and later changed its name to Trove, Inc. These assets consisted primarily of TravelPost-specific web content, software components, customer information, web domain names, trademarks and trademark applications, contracts and goodwill associated with TravelPost. Mr. Slyngstad was the Chief Executive Officer and is a director of TravelPost, Inc. and General Catalyst Group V, L.P. and GC Entrepreneurs Fund V, L.P., both of which are affiliated with General Catalyst Partners, of which Joel E. Cutler, one of our directors, is managing director and cofounder, are stockholders of TravelPost, Inc. On March 5, 2010, we entered into the following agreements with The New Travelco, Inc. in connection with the transaction:

• Asset Purchase Agreement, which provides for the sale to The New Travelco, Inc. of certain assets in exchange for $3.6 million in cash, 800,000 shares of The New Travelco, Inc. common stock and the assumption by The New Travelco, Inc. of certain of our obligations. The purchase price was established through a combination of third-party appraisal efforts and negotiations between us and The New Travelco, Inc.

• Commercial Agreement, pursuant to which we granted to The New Travelco, Inc. a three-year license to reproduce and publicly display hotel reviews and hotel-related information in exchange for a monthly license fee of $50,000 for the term of the license.

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• Common Stock Purchase Agreement, providing for the transfer to us of 800,000 shares of The New Travelco, Inc. common stock referred to above and under which we agreed to a lock-up period of 180 days following The New Travelco, Inc.’s first firm commitment underwritten public offering of its common stock.

• Patent License Agreement, pursuant to which we granted The New Travelco, Inc. a royalty-free and perpetual license to use certain processes for the operation of the travelpost.com website and associated domain names.

• Software License Agreement, pursuant to which we granted The New Travelco, Inc. a royalty-free and perpetual license to use certain computer programs in connection with the operation of the travelpost.com website and related domain names.

• Right of First Refusal and Co-Sale Agreement, pursuant to which we agreed to certain preemptive rights in favor of The New Travelco, Inc. with respect to its shares of common stock held by us. Mr. Slyngstad, General Catalyst Group V, L.P., GC Entrepreneurs Fund V, L.P. and certain other stockholders of The New Travelco, Inc. were additional parties to the agreement.

• Voting Agreement, under which we agreed to vote shares of The New Travelco, Inc.’s capital stock held by us in favor of the election of certain individuals as directors of The New Travelco, Inc. in accordance with the provisions of the agreement. Mr. Slyngstad, General Catalyst Group V, L.P., GC Entrepreneurs Fund V, L.P. and certain other stockholders of The New Travelco, Inc. were additional parties to the agreement.

Stockholders’ Agreement

On May 6, 2010, in connection with our acquisition of swoodoo, we entered into a Stockholders’ Agreement with certain holders of our convertible preferred stock and our common stock, including funds affiliated with General Catalyst Partners, funds affiliated with Sequoia Capital, of which Michael Moritz, one of our directors, is a partner, funds affiliated with Accel Partners, of which Hendrik W. Nelis, another of our directors, is a partner, Oak Investment Partners, one of our stockholders, Mr. Hafner, Mr. English and Dr. Christian W. Saller, our Managing Director for Europe. The requisite parties have agreed that this agreement will terminate upon the consummation of this offering. Among other things, the agreement, as amended to date, provides for the following:

• it gives us and certain of our stockholders the right of first refusal with respect to a sale of any of the shares of our common stock issued to Dr. Saller and other former swoodoo stockholders in connection with the acquisition, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering;

• it obligates Dr. Saller and other holders of the shares of our common stock issued in connection with the acquisition, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, to vote their shares for the election of the members of our board of directors consistent with the terms of our Sixth Amended and Restated Stock Restriction and Co-Sale Agreement; and

• it provides that, in the event of an approved sale of us, Dr. Saller and other holders of the shares of our common stock issued in connection with the acquisition, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, shall be required to vote their shares in favor of the sale.

Stock Restriction and Co-Sale Agreement

On December 22, 2011, we entered into the Sixth Amended and Restated Stock Restriction and Co-Sale Agreement with certain holders of our convertible preferred stock and our common stock, including certain funds affiliated with General Catalyst Partners, Sequoia Capital and Accel Partners, respectively, Oak Investment

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Partners, Mr. Slyngstad, Mr. Hafner, trusts of which Mr. Hafner is a trustee, Mr. English and trusts of which Mr. English is a trustee. The requisite parties have agreed that this agreement will terminate upon the consummation of this offering. Among other things, the agreement, as amended to date, provides for the following:

• it gives us and the preferred stockholders party to the agreement a right of first refusal with respect to proposed sales by certain holders of shares of KAYAK common stock listed in the agreement, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, to third parties;

• it establishes the composition of our board of directors;

• it provides that, in the event of an approved sale of our company, the parties to the agreement shall also be obligated to vote in favor of the sale; and

• it gives Oak Investment Partners the right to designate a board observer.

Investor Rights Agreement

On March 22, 2010, we entered into the Sixth Amended and Restated Investor Rights Agreement with certain of our investors referred to therein and our founders group, consisting of Mr. Hafner and trusts of which Mr. Hafner is a trustee and Mr. English and trusts of which Mr. English is a trustee. The investors include funds affiliated with General Catalyst Partners, funds affiliated with Sequoia Capital, funds affiliated with Accel Partners, Oak Investment Partners, Messrs. Slyngstad, Hafner and English. Among other things, the agreement, as amended to date, provides for the following:

• it provides certain holders of shares of our convertible preferred stock and common stock, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, with certain demand, “piggyback” and short-form registration rights, subject to lock-up arrangements;

• it provides for indemnification for certain liabilities in connection with a registration of our securities; and

• it establishes certain restrictions with respect to the transfer and issuance of our capital stock, including a right of first refusal in favor of certain investors and our founders group with respect to the issuance of certain securities by us, and it contains other restrictions, including limitations on our ability to incur debt, except for indebtedness under certain specified loan arrangements; however, these restrictions will automatically terminate upon the completion of this offering.

Election and Amendment Agreement

On April 19, 2012, we entered into the Election and Amendment Agreement with the holders of a majority of our capital stock. In addition to providing for the concurrent private placements which are described in the section of this prospectus titled “Concurrent Private Placements,” the Election and Amendment Agreement amended our Stockholders’ Agreement, Stock Restriction and Co-Sale Agreement and Investor Rights Agreement, and included an election by such stockholders under, and consent to an amendment to, our certificate of incorporation. The effect of such election and amendments is, among other things, to cause all shares of our convertible preferred stock to convert into shares of Class B common stock concurrently with the closing of any initial public offering that is completed pursuant to a registration statement which becomes effective prior to December 31, 2012, regardless of the initial public offering price in such offering. Pursuant to such election and amendments, the stockholders have also waived certain potential preemptive and anti-dilution related rights which they may have had upon completion of this offering and the concurrent private placements, and are causing the amended Stockholders’ Agreement and Stock Restriction and Co-Sale Agreement, and certain

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provisions of the amended Investor Rights Agreement, to automatically terminate upon the completion of this offering.

Services Agreement with ITA Software, Inc.

On March 3, 2005, we entered into a Services Agreement with ITA Software, Inc., or ITA, of which Mr. Cutler was a director and funds affiliated with General Catalyst Partners are 10% stockholders, for the licensing to us of airline faring engine software. The agreement was subsequently amended on July 18, 2007, March 11, 2008 and January 1, 2009. We paid ITA an initial payment of $166,666 followed by a monthly service fee based on the number of queries performed, subject to a minimum of $83,333 per month, a software maintenance and operation fee of $225 per hour and a hardware fee per month of $1,450 per dual processor server used.

On March 11, 2008, in addition to our arrangement with ITA, we agreed to assume payment obligations of SideStep to ITA following our acquisition of SideStep. On January 1, 2009, we agreed to amend the fee schedule as follows: to increase the monthly service fee to a minimum of $500,000 for the period until January 1, 2010, and a minimum of $583,333 per month thereafter until our aggregate payments for 2012 equal certain agreed-upon amounts, following which we would cease such monthly minimum payments until January 1, 2013, whereupon we have agreed to pay a minimum monthly fee to be calculated based upon the number of queries performed in 2012. For the period from January 1, 2012 through December 31, 2012, we have an estimated minimum commitment of approximately $7 million related to this agreement. We are unable to estimate our calendar year 2013 minimum commitment at this time.

During the past fiscal year, none of our executive officers served as a member of the board of directors or compensation committee, or other committee serving an equivalent function, of any entity that has one or more executive officers who served as members of our board of directors or our compensation committee. None of the members of our compensation committee is an officer or employee of KAYAK, nor have they ever been an officer or employee of KAYAK.

Code of Business Conduct and Ethics

We adopted a code of business conduct and ethics that applies to all of our employees, officers, directors and agents, including those officers responsible for financial reporting. Upon completion of the offering, our code of business conduct and ethics will be available on our website at KAYAK.com, the contents of which are not incorporated herein. Any amendments to the code, or any waivers of its requirements, will be disclosed on our website.

Board Leadership and Board’s Role in Risk Oversight

Mr. Jones, a non-employee, independent director, serves as Chairman of our board of directors. We support separating the position of Chief Executive Officer and Chairman to allow our Chief Executive Officer to focus on our day-to-day business, while allowing the Chairman to lead our board of directors in its fundamental role of providing advice to, and independent oversight of, management. Our board of directors recognizes the time, effort and energy that the Chief Executive Officer is required to devote to his position in the current business environment, as well as the commitment required to serve as our Chairman, particularly as our board of directors’ oversight responsibilities continue to grow. Our board of directors also believes that this structure ensures a greater role for the independent directors in the oversight of our company and active participation of the independent directors in setting agendas and establishing priorities and procedures for the work of our board of directors.

While our amended and restated by-laws and our corporate governance guidelines to be in effect upon completion of this offering will not require that our Chairman and Chief Executive Officer positions be separate,

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our board of directors believes that having separate positions and having an independent outside director serve as Chairman is the appropriate leadership structure for us at this time and demonstrates our commitment to good corporate governance.

Risk is inherent with every business and we face a number of risks as outlined in the “Risk Factors” section of this prospectus. Management is responsible for the day-to-day management of risks we face, while our board of directors, as a whole and through its audit committee, is responsible for overseeing our management and operations, including overseeing its risk assessment and risk management functions. Our board of directors expects to delegate responsibility for reviewing our policies with respect to risk assessment and risk management to our audit committee through its charter. Our board of directors believes that this oversight responsibility can be most efficiently performed by our audit committee as part of its overall responsibility for providing independent, objective oversight with respect to our accounting and financial reporting functions, internal and external audit functions and systems of internal controls over financial reporting and legal, ethical and regulatory compliance. Our audit committee will regularly report to our board of directors with respect to its oversight of these important areas.

Compensation Policies and Practices and Risk Management

We consider in establishing and reviewing our compensation philosophy and programs, whether such programs encourage unnecessary or excessive risk taking. Base salaries are fixed in amount and, consequently, we do not see them as encouraging risk taking. Employees are also eligible to receive a portion of their total compensation in the form of annual cash bonus awards. While the annual cash bonus awards focus on achievement of annual goals and could encourage the taking of short-term risks at the expense of long-term results, our annual cash bonus awards represent only a portion of eligible employees’ total compensation and are tied to both corporate performance measures and individual performance. We believe that the annual cash bonus awards appropriately balance risk with the desire to focus eligible employees on specific goals important to our success and do not encourage unnecessary or excessive risk taking.

We also provide our named executive officers and other senior managers long-term equity awards to help further align their interests with our interests and those of our stockholders. See “Executive Compensation—Compensation Discussion and Analysis” for additional discussion regard our compensation practice. We believe that these awards do not encourage unnecessary or excessive risk taking, since the awards are generally provided at the beginning of an employee’s tenure or at various intervals to award achievements or provide additional incentive to build long-term value and are generally subject to vesting schedules to help ensure that executives and senior managers have significant value tied to our long-term corporate success and performance.

We believe our compensation philosophy and programs encourage employees to strive to achieve both short- and long-term goals that are important to our success and building stockholder value, without promoting unnecessary or excessive risk taking. We review our compensation policies and practices periodically to determine whether such policies and practices are appropriate in light of our risk management objectives. We have concluded that our compensation philosophy and practices are not reasonably likely to have a material adverse effect on us.

Director Compensation

Historically, we have not provided cash retainers or fees to our directors for their service on the board of directors or its committees, or for attending board or committee meetings. In addition, our directors who are also employees receive no additional compensation or benefits for service on the board of directors or its committees. During fiscal year 2011, we did not grant any stock options to our non-employee directors. All members of our board of directors receive reimbursement of reasonable and documented costs and expenses incurred in connection with attending any meetings of our board of directors or any of our committees.

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Each of our nonemployee directors also has an indemnification agreement with us, which we will file as an exhibit to our registration statement of which this prospectus is a part. We also expect our directors to execute a new form of indemnification agreement prior to completion of this offering. See “Certain Relationships and Related Party Transactions—Indemnification of Officers and Directors” for more information.

To attract and retain the most highly qualified individuals to serve on our board of directors, those directors who are non-employees receive compensation for their service on our board of directors. Our executives who are members of our board of directors do not receive compensation for their service on our board of directors. Effective as of March 3, 2011, the nonemployee directors are paid:

• a base annual retainer of $50,000 in cash;

• an additional annual retainer of $10,000 in cash to members of the audit committee (other than the chairperson) and an annual retainer of $5,000 in cash to members of the compensation and nominating and governance committees (other than the chairpersons);

• an additional annual retainer of $25,000 in cash to the chair of the audit committee;

• an additional annual retainer of $10,000 in cash to the chair of the compensation committee and to the chair of the nominating and governance committee; and

• an additional annual retainer of $25,000 in cash to the chairperson of our board of directors.

Upon completion of this offering, we intend to provide each nonemployee director with equity compensation for service on our board of directors and committees. This compensation will consist of $175,000 in the form of restricted stock units of Class A common stock, based on the per share price of the Class A common stock sold in this offering, which shall vest quarterly over a two-year period from March 3, 2011. In addition, we will also continue to reimburse directors for reasonable expenses incurred to attend meetings of our board of directors or committees.

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EXECUTIVE COMPENSATION

Compensation Discussion and Analysis

The purpose of this compensation discussion and analysis section is to provide information about the material elements of compensation that are paid, awarded to, or earned by, our “named executive officers,” who consist of our principal executive officer, principal financial officer and our three other most highly compensated executive officers. For fiscal year 2011, our named executive officers, were:

• Daniel Stephen Hafner, President, Chief Executive Officer and Director;

• Willard H. Smith, Chief Financial Officer;

• Melissa H. Reiter, Senior Vice President, Finance and Investor Relations;

• Paul M. English, Chief Technology Officer and Director;

• Karen Ruzic Klein, General Counsel and Secretary; and

• Robert M. Birge, Chief Marketing Officer.

Mr. Smith’s employment with us ended on March 16, 2012, and Ms. Reiter was named Chief Financial Officer at that time.

Historical Compensation Decisions

We are a privately held company with a relatively small number of stockholders, including our principal stockholders, Sequoia Capital, General Catalyst Partners, Accel Partners and Oak Investment Partners. As a result, we have not previously been subject to any stock exchange listing or SEC rules requiring a majority of our board of directors to be independent or relating to the formation and functioning of board committees. Most, if not all, of our prior compensation policies and determinations, including those made for fiscal year 2011, have been the product of discussions between our Chief Executive Officer, our Chief Technology Officer and our existing compensation committee and board of directors.

Upon completion of this offering, we expect that our compensation committee will review our existing compensation approach to determine whether such approach is appropriate given that we will be a public company. Accordingly, the compensation paid to our named executive officers for fiscal year 2011 is not necessarily indicative of how we will compensate our named executive officers in the future.

Compensation Philosophy and Objectives

Our board of directors, in consultation with our compensation committee, reviews and approves the compensation of our named executive officers and oversees and administers our executive compensation approach and initiatives. Our executive compensation approach is based upon a philosophy that is designed to:

• attract and retain talented and experienced executives in our industry;

• reward executives whose knowledge, skills and performance are critical to our success;

• align the interests of our executive officers and stockholders by motivating executive officers to increase stockholder value and rewarding executive officers when stockholder value increases; and

• recognize the contributions each executive officer makes to our success.

The board of directors meets outside the presence of all of our named executive officers, except Ms. Klein, our General Counsel and Secretary, to consider appropriate compensation for our Chief Executive Officer and Chief Technology Officer. For all other named executive officers, the board of directors meets outside the presence of all named executive officers except our Chief Executive Officer, Chief Technology Officer and our General Counsel and Secretary, and further meets outside the presence of Ms. Klein when her compensation is being considered.

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Historically, compensation has been highly individualized, the result of arm’s-length negotiations and based on a variety of informal factors including, in addition to the factors listed above, our financial condition and available resources, our need for a particular position to be filled and the compensation levels of our other executive officers. As a result, our compensation committee and board of directors historically have applied their discretion to make compensation decisions and set the compensation for each named executive officer on an individual basis.

Upon completion of this offering, we expect that our Chief Executive Officer and Chief Technology Officer will review annually with the compensation committee each named executive officer’s performance and recommend appropriate base salary, cash performance awards and grants of equity incentive awards. Based upon these recommendations, and in consideration of the objectives described above and the principles described below, the compensation committee will approve the annual compensation packages of our named executive officers other than our Chief Executive Officer and Chief Technology Officer. The compensation committee, or the full board of directors upon recommendation of the compensation committee, will also annually analyze the performance of our Chief Executive Officer and Chief Technology Officer and approve their annual compensation packages based on its assessment of their performance.

Elements of Compensation

Our current executive compensation approach, which was set by our compensation committee and board of directors, consists of the following components:

• base salary;

• annual bonus awards consisting of cash or restricted stock awards, linked to corporate and individual performance;

• periodic grants of stock options and restricted stock awards; and

• other executive benefits.

Executive compensation includes both fixed compensation (base salary and benefits) and variable compensation (annual bonus and equity grants). Each component is linked to one or more of the compensation philosophy objectives listed above.

Fixed compensation is designed to induce talented executives to join or remain with us, while variable cash incentive awards are tied specifically to the achievement of our annual financial objectives and individual performance. Bonus amounts generally relate to the scope of responsibility for each named executive officer. Our bonus awards are designed to align each executive’s annual goals for his or her respective area of responsibility with the financial goals of the entire business.

The other element to variable compensation is equity awards, including stock option awards and restricted stock awards. Our Third Amended and Restated 2005 Equity Incentive Plan was adopted by our board of directors to award equity-based compensation, including stock options and restricted stock to executive officers and other key employees. The grants awarded under our Third Amended and Restated 2005 Equity Incentive Plan have no public market and no certain opportunity for liquidity until the completion of this offering, making them inherently long-term compensation. We expect to discontinue granting new awards under our Third Amended and Restated 2005 Equity Incentive Plan and adopt a 2012 Equity Incentive Plan, which will be in effect upon completion of this offering.

In the future, the compensation committee and the board of directors may engage and seek the input of consultants to evaluate our compensation packages and may formally benchmark executive compensation against a peer group of comparable companies.

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Base Salary

Historically, base salary has been the primary component of our compensation packages as it provides a constant and consistent source of income to our named executive officers. The initial base salary for each of our named executive officers was set in his or her employment agreement when the named executive officer commenced employment with us. Typically, base salaries are reviewed annually by our compensation committee and board of directors with input from our Chief Executive Officer and Chief Technology Officer, for base salaries other than the Chief Executive Officer and Chief Technology Officer, and may be increased depending on business circumstances and individual situations. Base salary also affects bonus awards as bonus awards for most employees, including named executive officers, are typically based on a percentage of base salary. Upon the completion of this offering, in determining base salaries of our named executive officers, the compensation committee and board of directors may also consider recommendations by compensation consultants, formal benchmarking against a particular set of comparable companies or survey data, or a combination of these factors.

In fiscal year 2011, our named executive officers received the following in base salary: $300,000 for Mr. Hafner; $275,000 for Mr. Smith; $260,000 for Ms. Reiter; $300,000 for Mr. English; $260,000 for Ms. Klein; and $320,000 for Mr. Birge.

Bonus Awards

Our board of directors, with input from our compensation committee and our Chief Executive Officer and Chief Technology Officer, other than for their own bonuses, determines annual cash bonus pool available for awards to employees, including our named executive officers. The annual cash bonuses are intended to reward the achievement of corporate objectives linked to our financial results. Prior to fiscal year 2011, we offered employees, including named executive officers the choice to take bonuses awarded either in cash or in a comparable number of shares of restricted common stock. We believe that our bonus awards help us attract and retain qualified and highly skilled employees and reward and motivate those who have had a positive impact on corporate results.

Historically, on an annual basis, our board of directors typically sets aside a bonus pool for executive officers and key employees with bonuses paid out, if at all, at the discretion of the board of directors, for Mr. Hafner and Mr. English, or by Mr. Hafner and Mr. English, for most other employees. Bonuses are typically based on positive performance and our achievement of certain financial and commercial targets determined by the board of directors prior to the beginning of each fiscal year. For our named executive officers, bonus targets, as a percentage of base salary or a maximum dollar amount, are set forth in the employment contract of each named executive officer. Actual bonus awards may differ from such target percentages, based on KAYAK’s achievement of corporate targets and the individual’s contribution to such achievement of corporate performance.

In determining bonuses for fiscal year 2009, which were paid in fiscal year 2010, the board of directors determined the bonus amounts for Mr. Hafner and Mr. English and established the bonus pool for all other employees, including the other named executive officers. In setting these amounts the following financial and corporate achievements, among other items, were considered:

• we substantially met our goals for number of queries and visits for the year; and

• we substantially met our commercialization goals for the year, including our targets for revenues and adjusted earnings.

In particular, our target goals for number of queries and visits was 496 million and 473 million, respectively, and we achieved approximately 93% and 91% of these targets, respectively. Our target goals for revenues and adjusted earnings were $140 million and $28 million, respectively, and based on projected results evaluated by the board of directors in December 2009, we achieved approximately 82% and 79% of these targets, respectively. Adjusted earnings for this purpose represented Adjusted EBITDA plus bonus expense, bad-debt expense and miscellaneous other expenses incurred in 2010. These performance targets, which were used for compensation purposes only, were developed to incentivize management and were based on certain primary objectives of our

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internal business plan. They were not used by management or the board of directors for other purposes. All named executive officers were subject to the same performance goals for the year.

We failed to fully meet our target financial and corporate goals for the year, and as a result, the bonuses paid for fiscal year 2009 were 90% of the targets set in each named executive officer’s employment agreement. In setting this bonus amount our board of directors evaluated the degree to which bonus targets were not achieved. In making this evaluation the board of directors estimated that bonus targets were generally achieved at approximately a 79% to 93% level, and therefore determined that paying bonuses to Messrs. Hafner and English and funding the bonus pool at the 90% level would be appropriate. Based on this assessment, Mr. Hafner received $405,000; Mr. English received $405,000; Ms. Klein received $200,000 and Mr. Birge received $184,998. Of such amounts, Mr. Hafner elected to receive $112,663 of this amount in 9,979 shares of restricted common stock, Mr. English elected to receive $116,626 of this amount in 10,330 shares of restricted common stock, Ms. Klein elected to receive $24,996 of this amount in 2,214 shares of restricted common stock and Mr. Birge elected to receive $184,998 of this amount in 16,386 shares of restricted common stock. In each of these cases, the dollar amount of bonuses forgone by the named executive officer was equal to the fair market value of the shares of restricted stock they received in exchange for the foregone amount. Ms. Reiter started with us in November 2009 and as such was not subject to the bonus plan. However, Ms. Reiter’s employment agreement with us provided for a fixed bonus amount of $50,000.

In determining bonuses for fiscal year 2010, which are paid in fiscal year 2011, the board of directors determined the bonus amounts for Mr. Hafner and Mr. English and established the bonus pool for all other employees, including the other named executive officers. In setting these amounts the following financial and corporate achievements, among other items, were considered:

• we substantially met our goal for number of queries for the year; and

• we substantially met our commercialization goals for the year, including our targets for revenues and adjusted earnings.

During 2010, in an effort to more directly align Mr. Hafner’s and Mr. English’s bonus awards to our financial performance, the board of directors established different performance goals for Mr. Hafner and Mr. English compared to our other employees.

Specifically, the board of directors, in establishing the bonus pool for all employees other than Mr. Hafner and Mr. English, set a target goal for number of queries of 595 million. We achieved approximately 107% of this target goal. Our target goals for revenues and adjusted earnings (representing Adjusted EBITDA plus bonus expense accrued in 2010) were $147 million and $37 million, respectively. We achieved 116% of our revenue goal and 96% of our adjusted earnings target in 2010. The board of directors approved an additional investment in brand marketing expense during the fourth quarter of 2010, which was factored into their decision to consider our adjusted earnings target as met for the year ended December 31, 2010.

For Mr. Hafner and Mr. English, the board of directors set 2010 target goals of $147 million and $37 million for revenue and Adjusted EBITDA, respectively. In addition, the board of directors set threshold targets of $140 million and $25 million for revenue and Adjusted EBITDA, respectively, for Mr. Hafner and Mr. English, at which point they would be entitled to at least 75% of their bonus targets. Our board of directors has determined that we substantially met or exceeded these goals at the higher target levels.

The 2010 compensation performance targets were used solely for determining compensation of our named executive officers and were not used by management or the board of directors for other purposes.

As a result of our financial performance and the level at which we met our corporate operating goals for the year, our board of directors awarded the following cash bonus amounts for fiscal year 2010, which were paid in 2011: Ms. Reiter received $150,000; Ms. Klein received $280,000; and Mr. Birge received $350,000. Our board of directors also determined that, at the time of payment, each of the named executive officers would be entitled

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to exchange some or all of their bonus amounts for shares of our common stock having a fair value equal to the bonus amount foregone. Of the bonus amounts awarded for fiscal year 2010, Mr. Birge elected to receive $149,600 of this amount in 8,500 shares of restricted stock and Ms. Klein elected to receive $24,992 of this amount in 1,420 shares of restricted stock.

In fiscal year 2010, the board of directors revised the maximum bonus amounts Mr. Hafner and Mr. English could receive. As a result Messrs. Hafner and English were entitled to earn a bonus amount of up to $345,000 each. Subsequent to our 2010 fiscal year end, each of Messrs. Hafner and English elected not to receive any such bonus amounts.

In determining bonuses for fiscal year 2011, which were paid in fiscal year 2012, the board of directors established the bonus pool for all employees other than Mr. Hafner and Mr. English. In setting these amounts the following financial and corporate achievements, among other items, were considered:

• We exceeded our goal for total number of queries for the year;

• We substantially met our goal for number of hotel queries during the year; and

• We substantially met our commercialization goals for the year.

In general, the same primary objectives used for establishing our 2010 bonus awards were used to establish bonus awards in 2011. However, during 2011, the board of directors did not establish performance goals for Mr. Hafner and Mr. English. During the beginning of fiscal year 2011, the board of directors determined that Mr. Hafner and Mr. English, in accordance with their employment agreements, would each be eligible to receive a bonus up to $345,000. The board of directors further determined that the bonus amount awarded to Mr. Hafner and Mr. English, if any, would be established after fiscal year 2011. The board of directors adopted this approach with respect to Mr. Hafner’s and Mr. English’s potential bonus amounts in and effort to award each officer’s performance in consideration of our overall success and performance during the year.

With respect to all employees other than Mr. Hafner and Mr. English, the board of directors set a target goal for total number of queries of 853 million and number of hotel queries of 97 million. We achieved approximately 105% and 98%, respectively, of these target goals. Our target goals for revenues and adjusted earnings (representing Adjusted EBITDA plus bonus expense accrued in 2011) were $242 million and $56 million, respectively. We achieved 93% of our revenue goal and 100% of our adjusted earnings target in 2011.

As in 2010, the 2011 compensation performance targets were used solely for determining compensation of our named executive officers and were not used by management or the board of directors for other purposes.

As a result of our financial performance and the level at which we substantially met or exceeded our corporate operating goals for the year, our board of directors awarded the following cash bonus amounts for fiscal year 2011, which were paid in 2012: Mr. Smith received $84,000; Ms. Reiter received $175,000; Ms. Klein received $275,000; and Mr. Birge received $375,000. Unlike in previous years, our employees, including our named executive offers were not provided an opportunity to exchange all or a portion of their bonus awards for shares of our common stock.

Upon completion of this offering, we expect our board of directors or compensation committee to establish a bonus plan comparable to other public companies in our industry. We may use formal bench-marking efforts to establish such a bonus plan.

Equity-Based Compensation

Our board of directors believes that equity-based compensation is an important component of our executive compensation approach and that providing a significant portion of our named executive officers’ total compensation package in equity-based compensation aligns the incentives of our named executive officers with the interests of our stockholders and with our long-term corporate success. Additionally, our compensation committee and board of directors believe that equity-based compensation awards enable us to attract, motivate,

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retain and adequately compensate executive talent. To that end, we have awarded equity-based compensation in the form of options to purchase shares of our common stock, which will automatically become options to purchase shares of our Class B common stock upon the completion of this offering, and shares of restricted stock. Our compensation committee and board of directors believe these forms of equity-based compensation provide our named executive officers with a significant long-term interest in our success by rewarding the creation of stockholder value over time.

Stock Options

Generally, each named executive officer is provided with a stock option grant when he or she joins KAYAK based upon his or her position with us. Each such initial stock option grant generally vests over the course of four years with 25% of the shares vesting on the first anniversary of the grant date or employment date, as applicable, and the remainder of the shares vesting in 36 equal monthly installments. In addition to stock options granted upon commencement of employment with us, our compensation committee or board of directors may grant additional stock options from time to time to retain our executives and to recognize the achievement of corporate and individual goals. Stock options awarded as retention grants or in recognition of special achievements generally vest in 48 equal monthly installments. The term of stock options issued under our Third Amended and Restated 2005 Equity Incentive Plan is generally ten years from the date of grant.

Stock options are granted with an exercise price equal to or greater than the fair value of our stock on the applicable date of grant. To date, the fair value of the common stock underlying our stock option grants was determined by our board of directors, with the assistance of management. See “Management’s Discussion and Analysis of Financial Conditions and Results of Operations—Critical Accounting Policies and Estimates—Common Stock Valuations” for additional discussion on how we value our common stock.

After the completion of this offering, fair value will be based on the closing price of our Class A common stock on The NASDAQ Stock Market on the date of grant.

In general, stock option grants to our named executive officers have been determined at the discretion of our board of directors. In addition, our board of directors has also considered a named executive officer’s current position with us, the size of his or her total compensation package and the amount of existing vested and unvested stock options, if any, then held by the executive officer. Upon completion of this offering, the compensation committee intends to undertake primary responsibility for this function and to formalize this process with annual grants and may use formal bench-marking efforts to determine grant amounts.

Restricted Stock

In addition to grants of stock options, we have also awarded shares of restricted stock to our executive officers and key employees in lieu of all or a portion of their annual merit-based cash bonus and in recognition of special contributions and achievements. We believe that the use of restricted stock awards as a portion of our long-term equity-based compensation program may have the benefit of incentivizing our executive officers and key employees to remain with us and to continue performing at a high level even during periods in which our stock price is down and previously granted stock options may have little or no realizable value.

Fiscal Year 2011 Stock Option and Restricted Stock Awards

In fiscal year 2011, we approved grants of restricted stock awards to Mr. Birge and Ms. Klein. These restricted stock grants represent the portion of the 2010 merit-based bonuses of those named executive officers who elected to receive restricted stock in lieu of cash. The shares of restricted stock awards representing such grants were issued to the recipients in January 2011. In addition to these restricted stock grants, we also awarded an option to Mr. Smith to acquire 200,000 shares of our common stock. This option award was made to Mr. Smith in connection with the commencement of his employment as our Chief Financial Officer on June 6, 2011.

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The stock options and restricted stock awards were granted in accordance with our Third Amended and Restated 2005 Equity Incentive Plan as follows:

Name	Grant Date		Number of Securities Underlying Options(#)		Exercise Price of Option Awards ($/Sh)		Number of Shares of Restricted Stock Received in Lieu  of Non-Equity Incentive Plan Compensation(1)		Value per Share of Restricted Stock Received in Lieu of Non-Equity Incentive Plan Compensation(1)
Willard H. Smith		6/7/2011		200,000	$	21.00		—		—
Karen Ruzic Klein		1/31/2011		—		—		1,420	$	17.60
Robert M. Birge		1/31/2011		—		—		8,500	$	17.60

(1) With regard to fiscal year 2010 bonuses paid in 2011, employees were given the opportunity to take some or all of their non-equity incentive compensation or bonuses in shares of our restricted common stock in lieu of a cash payment. Employees were not able to receive restricted stock in lieu of fiscal year 2011 cash bonuses paid in 2012.

The number of shares of common stock underlying each stock option grant, which will automatically become shares of Class B common stock underlying each such stock option grant upon the completion of this offering, was determined by our board of directors based upon the outstanding equity grants held both by the individual and by our named executive officers as a group, total compensation, performance, the vesting dates of outstanding grants, tax and accounting costs, potential dilution and other factors. The exercise price of the stock options equals at least 100% of the fair market value on the grant date in accordance with the terms of the Third Amended and Restated 2005 Equity Incentive Plan. The number of shares underlying each restricted stock grant to executives electing to receive restricted stock in lieu of part or all of their 2010 merit-based bonus was determined based on the fair market value of our common stock on the grant date and the dollar amount of the executive’s cash bonus that the executive elected to receive in the form of restricted stock.

Other Executive Benefits

We provide the following benefits to our named executive officers to attract and retain qualified and highly skilled executives:

• health and dental insurance;

• long-term disability, life insurance and accidental death and dismemberment insurance plans;

• participation in our flexible spending plan;

• participation in the our 401(k) plan;

• paid vacation as provided in each named executive officer’s employment contract; and

• directors’ and officers’ liability insurance.

With the exception of our directors’ and officers’ liability insurance, which we view as integrally and directly related to the performance of the applicable officer’s duties, all benefits available to our named executive officers are generally available to all of our employees.

Severance and Change-in-Control Benefits

We have entered into employment agreements with the named executive officers that contain severance benefits, the terms of which are described under the heading “—Employment Agreements and Potential Payments Upon Termination or Change-in-Control.” We believe these severance benefits are essential elements of our executive compensation package by assisting in recruiting and retaining talented executives.

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Section 162(m) Compliance

Section 162(m) of the U.S. Internal Revenue Code of 1986, as amended, or the Code, limits us to a deduction for federal income tax purposes of no more than $1.0 million of compensation paid to certain executive officers in a taxable year. Compensation above $1.0 million may be deducted if it is “performance-based compensation” within the meaning of section 162(m) of the Code. Our board of directors believes that we should be able to continue to manage our executive compensation for our named executive officers so as to preserve the related federal income tax deductions, although individual exceptions may occur.

Summary Compensation Table

The following table sets forth certain information regarding compensation for fiscal years 2009, 2010 and 2011 awarded to or paid to our named executive officers.

Name and Principal Position	Year		Salary ($)		Bonus(4) ($)		Option Awards(1) ($)		Non-Equity Incentive Plan Compensation(3) ($)			All Other Compensation ($)			Total ($)
Daniel Stephen Hafner		2011	$	300,000	$	650,000	$	—	$	—		$	—		$	950,000
Chief Executive Officer & Cofounder		2010	$	300,000	$	—	$	1,317,060	$	—	(2)	$	—		$	1,617,060
		2009	$	225,000	$	—	$	—	$	405,000	(9)				$	630,000
Willard H. Smith(6)		2011	$	157,466	$	822	$	1,918,200	$	83,178		$	13,766	(7)	$	2,173,432
Chief Financial Officer
Melissa H. Reiter		2011	$	260,000	$	45,000	$	—	$	130,000		$	—		$	435,000
Senior Vice President Finance and Investor Relations		2010	$	222,500	$	20,000	$	1,117,752	$	130,000		$	—		$	1,490,252
		2009	$	36,660	$	70,000	$	—	$	—		$	16,284	(8)	$	122,944
Paul M. English		2011	$	300,000	$	650,000	$	—	$	—		$	—		$	950,000
Chief Technology Officer & Cofounder		2010	$	300,000	$	—	$	1,317,060	$	—	(2)	$	—		$	1,617,060
		2009	$	225,000	$	—	$	—	$	405,000	(9)	$	—		$	630,000
Karen Ruzic Klein		2011	$	260,000	$	15,000	$	—	$	260,000		$	—		$	535,000
General Counsel		2010	$	235,000	$	45,000	$	539,142	$	235,000	(5)	$	—		$	1,054,142
		2009	$	210,000	$	—	$	198,040	$	200,000	(9)	$	—		$	608,040
Robert M. Birge		2011	$	320,000	$	55,000	$	—	$	320,000		$	—		$	695,000
Chief Marketing Officer		2010	$	300,000	$	50,000	$	1,078,284	$	300,000	(5)	$	—		$	1,728,284
		2009	$	196,591	$	—	$	644,940	$	184,998	(9)	$	—		$	1,026,529

(1) Amounts included in “Option Awards” column do not reflect compensation actually received by the named executive officer but represent the grant date fair value of the award as computed in accordance with FASB ASC Topic 718. The valuation assumptions used in determining such amounts are described in “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Critical Accounting Policies and Estimates—Common Stock Valuations”.

(2) Subsequent to our 2010 fiscal year end, each of Messrs. Hafner and English elected not to receive any bonus amounts in respect of fiscal 2010.

(3) Amount represents non-equity incentive plan compensation payable in accordance with the named executive officer’s employment agreement with us. In 2011 and 2010, each of Mr. Hafner and Mr. English were entitled to earn up to $345,000, Mr. Smith was entitled to earn up to 60% of his base salary, of Ms. Klein and Mr. Birge were entitled to earn up to 100% of their base salary and Ms. Reiter up to 50% of her base salary, in non-equity incentive compensation. In 2009, Mr. Hafner, Mr. English, Ms. Klein and Mr. Birge were entitled to earn up to 200%, 200%, 100% and 100%, respectively, in non-equity incentive compensation.

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(4) Amounts represent bonus amounts in excess of non-equity incentive compensation target amounts that are provided for in each of the named executive officer employment agreements. Cash bonuses in excess of non-equity incentive compensation are awarded at the discretion of our board of directors and are based on our board of directors’ subjective assessments of the named executive officer’s performance and contributions to us.

(5) Employees were given the option to receive a portion of their 2010 merit-based bonus in restricted stock in lieu of cash. In connection with this option, Mr. Birge elected to receive 8,500 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2010. The fair market value of Mr. Birge’s shares on the date of issuance was $149,600 and was equal to the dollar value of non-equity incentive compensation forgone by Mr. Birge. Additionally, Ms. Klein elected to receive 1,420 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2010. The fair market value of Ms. Klein’s shares on the date of issuance was $24,992 and was equal to the dollar value of non-equity incentive compensation forgone by Ms. Klein.

(6) Mr. Smith’s employment with us commenced on June 6, 2011. Mr. Smith’s compensation amounts included in this table for fiscal year 2011, reflect actual compensation earned by Mr. Smith during the year. Mr. Smith’s employment with us ended on March 16, 2012, and Ms. Reiter was named Chief Financial Officer at that time.

(7) We reimbursed Mr. Smith for relocation expenses totaling $13,766.

(8) We reimbursed Ms. Reiter for relocation expenses totaling $16,284.

(9) Employees were given the option to receive a portion of their 2009 merit-based bonus in restricted stock in lieu of cash. Mr. Hafner elected to receive 9,979 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2009. The fair market value of Mr. Hafner’s shares on the date of issuance was $112,663 and was equal to the dollar value of non-equity incentive compensation forgone by Mr. Hafner. Mr. English elected to receive 10,330 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2009. The fair market value of Mr. English’s shares on the date of issuance was $116,626 and was equal to the dollar value of non-equity incentive compensation forgone by Mr. English. Ms. Klein elected to receive 2,214 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2009. The fair market value of Ms. Klein’s shares on the date of issuance was $24,996 and was equal to the dollar value of non-equity incentive compensation forgone by Ms. Klein. Mr. Birge elected to receive 16,386 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2009. The fair market value of Mr. Birge’s shares on the date of issuance was $184,998 and was equal to the dollar value of non-equity incentive compensation forgone by Mr. Birge.

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2011 Grants of Plan-Based Awards

The following table sets forth certain information regarding grants of plan-based awards to our named executive officers for fiscal year 2011.

Name	Grant Date		Date Approved by Board of Directors		Estimated Future  Payouts Under Non-Equity Incentive Plan Awards							All Other Stock Awards: Number of Shares of Stock (#)			All  other Option Awards: Number  of Securities Underlying Options (#)			Exercise or  Base Price of Option Awards ($/Sh)		Grant Date Fair  Value of Stock and Option Awards ($)(4)
					Threshold ($)		Target ($)(1)			Maximum ($)
Daniel Stephen Hafner						—		—			—
Willard H. Smith						—	$	83,178	(3)		—
		6/7/2011		6/7/2011									—			200,000	(5)	$	21.00	$	1,918,200
Melissa H. Reiter						—	$	130,000			—
Paul M. English						—		—			—
Karen Ruzic Klein						—	$	260,000			—
		1/31/2011		12/8/2010									1,420	(2)		—			—	$	24,992
Robert M. Birge						—	$	320,000			—
		1/31/2011		12/8/2010									8,500	(2)		—			—	$	149,600

(1) Reflects target payouts with respect to amounts earned by each named executive officer pursuant to the terms of that officer’s employment agreement with us. While the amounts set forth are the target amounts included in the named executive officer’s employment agreements, our compensation committee and board of directors may exercise its discretion to award more or less than the target amount. Target amounts do not necessarily reflect amounts earned or paid, the actual amount earned by each named executive officer in 2011 is reported under the Non-Equity Incentive Compensation column and the Bonus column of the Summary Compensation Table.

(2) Amount represents number of restricted shares issued to the named executive officer in lieu of non-equity incentive plan compensation payable in accordance with the named executive officer’s employment agreement with us. Mr. Birge elected to receive 8,500 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2011. The fair market value of Mr. Birge’s shares on the date of issuance was $149,600 and was equal to the dollar value of non-equity incentive compensation forgone by Mr. Birge. Ms. Klein elected to receive 1,420 shares of our restricted common stock in lieu of non-equity incentive compensation earned in fiscal year 2011. The fair market value of Ms. Klein’s shares on the date of issuance was $24,992 and was equal to the dollar value of non-equity incentive compensation forgone by Ms. Klein.

(3) Amount is pro rated from June 30, 2011. As per his employment agreement, Mr. Smith was entitled to earn up to 60% of his salary as non-equity incentive compensation.

(4) Amounts represent the grant date fair value of the award as computed in accordance with FASB ASC Topic 718. The valuation assumptions used in determining such amounts are described in “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Common Stock Valuations”.

(5) The shares subject to this stock option vest with respect to 25% of the shares subject to such stock option on the first anniversary date of the date of hire and monthly over a three-year period at a rate of 1/36th per month thereafter. Vesting is contingent upon continued service.

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Outstanding Equity Awards at 2011 Fiscal Year-End

The following table sets forth certain information regarding outstanding equity awards for each of our named executive officers as of end of fiscal year 2011.

Name	Grant Date		Option Awards
			Number of Securities Underlying Unexercised Options (#) Exercisable		Number of Securities Underlying Unexercised Options (#) Unexercisable			Option Exercise Price ($)		Option Expiration Date
Daniel Stephen Hafner		4/29/2010		95,833		104,167	(1)	$	13.00		4/29/2020
Willard H. Smith		6/7/2011		—		200,000	(2)	$	21.00		6/7/2021
Melissa H. Reiter		10/20/2010		18,749		41,251	(1)	$	14.82		10/19/2020
		2/11/2010		54,166		45,834	(2)	$	11.29		2/11/2020
Paul M. English		4/29/2010		95,833		104,167	(1)	$	13.00		4/29/2020
Karen Ruzic Klein		10/20/2010		18,749		41,251	(1)	$	14.82		10/19/2020
		7/7/2009		120,833		79,167	(1)	$	7.50		7/6/2019
Robert M. Birge		10/20/2010		37,499		82,501	(1)	$	14.82		10/19/2020
		5/19/2009		96,874		53,126	(2)	$	7.50		5/19/2019

(1) The shares subject to these stock options vest monthly over a four-year period at a rate of 1/48th per month. Vesting is contingent upon continued service.

(2) The shares subject to this stock option vest with respect to 25% of the shares subject to such stock option on the first anniversary date of the date of hire and monthly over a three-year period at a rate of 1/36th per month thereafter. Vesting is contingent upon continued service.

Options Exercises and Stock Vested

The following table sets forth stock vested pursuant to awards of restricted stock for each of our named executive officers during the fiscal year 2011. None of our named executive officers exercised stock options during the fiscal year 2011.

Name	Stock Awards
	Number of Shares Acquired on Vesting (#)		Value Realized on Vesting ($)(1)
Daniel Stephen Hafner		—		—
Willard H. Smith		—		—
Melissa H. Reiter		—		—
Paul M. English		—		—
Karen Ruzic Klein		1,420	$	24,992
Robert M. Birge		8,500	$	149,600

(1) Amounts represent the fair market value of our common stock on the date of vesting times the number of shares of common stock vested on that date. The valuation assumptions used in determining the fair value of our common stock are described in “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Critical Accounting Policies and Estimates—Common Stock Valuations”.

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Pension Benefits

We do not sponsor defined benefit plans. Consequently, our named executive officers did not participate in, or have account balances in, qualified or nonqualified defined benefit plans. Our board of directors or compensation committee may elect to adopt qualified or nonqualified defined benefit plans in the future if it determines that doing so is in our best interest.

Nonqualified Deferred Compensation

We do not maintain nonqualified defined contribution plans or other deferred compensation plans. Consequently, our named executive officers did not participate in, or have account balances in, nonqualified defined contribution plans or other nonqualified deferred compensation plans. Our board of directors or compensation committee may elect to provide our executive officers and other employees with nonqualified defined contribution or other nonqualified deferred compensation benefits in the future if it determines that doing so is in our best interest.

Employment Agreements and Potential Payments Upon Termination or Change-in-Control

Employment Agreements

We have entered into employment agreements with each of our named executive officers as described below.

Daniel Stephen Hafner. On March 2, 2004, we entered into an executive employment agreement with Mr. Hafner, which was amended on March 1, 2007, June 26, 2008, April 29, 2010 and December 14, 2011. The agreement provides for an annual base salary of $300,000, subject to adjustment by the board of directors, and a bonus of $345,000. The agreement also provides for four weeks of paid vacation per year, reimbursement of reasonable business expenses, and participation in such other benefits programs as are provided to our executives generally.

Willard H. Smith. On May 11, 2011, we entered into an employment agreement with Mr. Smith. This agreement provided for Mr. Smith to receive an annual base salary of $275,000, subject to periodic review and adjustment by management, and an annual bonus of 60% of his base salary. The agreement provided for three weeks of paid vacation per year, reimbursement of reasonable business expenses, and participation in such other benefits programs as are provided to our executives generally. Mr. Smith’s employment with us ended on March 16, 2012. As part of his separation we agreed to pay Mr. Smith a lump sum amount of $261,000, representing six months salary and bonus. With respect to Mr. Smith’s termination, we also agreed to (i) accelerate stock option vesting with respect to 50,000 shares of our common stock, (ii) provide Mr. Smith a loan of up to $1,200,000 to be used solely for the exercise of such stock options, (iii) pay six months of COBRA subsidy and (iv) pay relocation expenses of up to $15,000.

Melissa H. Reiter. On November 1, 2010, we entered into an amended employment agreement with Ms. Reiter. This agreement provides for Ms. Reiter to receive an annual base salary of $260,000, subject to periodic review and adjustment by management, and an annual bonus of 50% of her annual base salary. The agreement provides for three weeks of paid vacation per year, reimbursement of reasonable business expenses, and participation in such other benefits programs as are provided to our executives generally. Ms. Reiter is also entitled to a bonus of $100,000 to be paid within 45 days of our initial public offering, provided that this amount must be repaid if Ms. Reiter terminates her employment with us within six months of our initial public offering.

Paul M. English. On March 2, 2004, we entered into an executive employment agreement with Mr. English, which was amended on March 1, 2007, June 26, 2008 and December 14, 2011. The agreement provides for an annual base salary of $300,000, subject to adjustment by the board of directors, and a bonus of $345,000. The agreement also provides for four weeks of paid vacation per year, reimbursement of reasonable business expenses and participation in such other benefits programs as are provided to our executives generally.

Karen Ruzic Klein. On October 22, 2007, we entered into an employment agreement with Ms. Klein, which has been reviewed and adjusted annually by management and as of January 1, 2011, provided for an annual base

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salary of $260,000, and an annual bonus of 100% of her annual base salary. The agreement provides for three weeks of paid vacation per year, reimbursement of reasonable business expenses, and participation in such other benefits programs as are provided to our executives generally.

Robert M. Birge. On April 9, 2009, we entered into an employment agreement with Mr. Birge, which has been reviewed and adjusted annually by management and as of January 1, 2011, provided for an annual base salary of $320,000, and an annual bonus of 100% of his annual base salary. The agreement provides for three weeks of paid vacation per year, reimbursement of reasonable business expenses, and participation in such other benefits programs as are provided to our executives generally.

Termination of Employment Agreements and Change-in-Control Arrangements

The information below describes and quantifies certain compensation that would become payable under each named executive officer’s employment agreement if, as of December 31, 2011, their employment agreements were in effect and their employment with us had been terminated. Due to the number of factors that affect the nature and amount of any benefits provided upon the events discussed below, any actual amounts paid or distributed may be different. Factors that could affect these amounts include the timing during the year of any such event.

The employment agreements for Mr. Hafner and Mr. English provide for compensation in the event of termination of their employment due to death or disability, without cause, and by the executive for good reason. Both Mr. Hafner’s and Mr. English’s employment agreements contain the following termination-related provisions:

• Termination Due to Death or Disability. Severance payments equal to any unpaid portion of the executive’s base salary through the date of death or disability, any accrued but unused vacation time through the date of termination, and reimbursement of business expenses incurred through such date. In addition, the executive would be entitled to any unpaid bonuses from prior years, and the pro rata portion of any bonus earned but unpaid for the year during which the agreement is terminated.

• Termination Without Cause or for Good Reason. Severance payments equal to the executive’s base salary through the date of termination, and for six months thereafter, to be paid in accordance with our standard payroll practices, any accrued but unused vacation time through the date of termination, and reimbursement of business expenses incurred through such date. If the employee elects to continue medical insurance coverage after termination, KAYAK would pay COBRA payments during the six-month severance period, or until the employee accepted other employment, if sooner. In addition, the executive would be entitled to any unpaid bonuses from prior years, and the pro rata portion of any bonus earned but unpaid for the year during which the agreement is terminated.

• Termination by the Employee other than for Good Reason. Any salary earned but unpaid through the date of termination, any earned but unpaid bonuses from prior years, any accrued by unused vacation time through the date of termination, and reimbursement of business expenses incurred through such date.

• Conditions to Severance. Receipt of any severance and benefits upon termination without cause or for good reason is conditioned on the executive signing a release and waiver of claims in a form satisfactory to us.

• Noncompetition. Mr. Hafner’s and Mr. English’s executive employment agreements also require each of them to enter into our standard employee noncompetition, nondisclosure and developments agreement, which generally prohibit employees from disclosing confidential information and trade secrets, soliciting any employee, vendor or customer for one year following termination of their employment and working with or for any competing companies during their employment and for one year thereafter. In addition to Mr. Hafner and Mr. English, our other named executive offers have also entered into our standard employee noncompetition, nondisclosure and developments agreement.

• “For Cause.” Under these employment agreements, “cause” generally means (i) failure or refusal of the employee to perform his reasonably assigned duties to KAYAK; (ii) a material breach of the employment agreement or the employee noncompetition, nondisclosure and developments agreement described above, or any other agreement between the employee and KAYAK relating to the

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employee’s employment with KAYAK; (iii) embezzlement or misappropriation of KAYAK’s assets or property; (iv) gross negligence, misconduct, neglect of duties, theft dishonesty or fraud with respect to KAYAK, or a breach of fiduciary duties to KAYAK; or (v) indictment or conviction of felony or any crime involving moral turpitude, including a plea of guilty or nolo contendere.

• “Good Reason.” Under these employment agreements, “good reason” generally means (i) mutual agreement between us and the employee that good reason exists; (ii) a material violation by us of the employee’s executive employment agreement; (iii) demotion of the executive, without his prior consent, to a position that does not include significant managerial responsibilities; or (iv) reduction in base salary, other than in connection with and substantially proportionate to a general salary reduction that applies to our executive officers generally.

The employment agreements for Mr. Smith, Ms. Reiter, Ms. Klein and Mr. Birge each provide for compensation in the event of involuntary termination of their employment other than for cause. Under these employment agreements, in the event of involuntary termination of their employment other than for cause, each would be entitled to receive six months’ base salary plus the pro rata portion of any bonus earned but unpaid for the year and payment of COBRA insurance coverage for the duration of the six month severance term. In addition, Ms. Reiter is entitled to receive six months base salary and a pro rated bonus as severance if she is not named Chief Financial Officer by December 31, 2012, and she elects to terminate her employment with us at any time following December 31, 2012. Ms. Reiter is also entitled to a bonus of $100,000 to be paid within 45 days of our initial public offering, provided that this amount must be repaid if Ms. Reiter terminates her employment with us within six months of our initial public offering.

Under both our Third Amended and Restated 2005 Equity Incentive Plan and our 2004 Stock Incentive Plan, in the event of a merger or consolidation, other than a merger or consolidation in which our stockholders will hold more than 50% of the equity interests of the surviving entity immediately following such merger or consolidation, the sale of all or substantially all of our assets, or the acquisition by any person of securities representing more than 50% of the total combined voting power of KAYAK, all of which are referred to in this prospectus as a change of control, (i) 50% of the unvested portion of all options outstanding as of the date of the change of control will vest and become exercisable as of such date and (ii) the risk of forfeiture (as defined in the plans) or repurchase right applicable to 50% of any restricted stock grant will lapse, and 50% of the stock relating to such awards will become free of all restrictions and become fully vested and transferable, as of the date of the change in control. The remaining outstanding options and restricted stock subject to a risk of forfeiture or repurchase right will vest and become exercisable upon:

• the termination of the plan participant’s employment or other association with us and our affiliates by us without cause (as defined in the plans) or by the plan participant for good reason (as defined in the plans) or upon the plan participant’s position, duties, authority or responsibilities being materially diminished, other than on a temporary basis, within one year after the date of such change of control; or

• the date a change of control occurred if such termination or diminution occurs within 60 days prior to the date on which the change of control occurred, and the affected plan participant demonstrates that such termination or diminution was at the request of a third party that took actions to effect the change of control or otherwise arose in connection with or anticipation of the change of control.

In the event of a change of control, outstanding awards under both plans will be subject to the terms of any agreement of merger or reorganization that effects the change of control.

Under certain of the individual stock option agreements and restricted stock agreements entered into with each of our named executive officers, we have the right to repurchase any shares of common stock acquired by the executive pursuant to the exercise of stock options for a period of 90 days following the later of the termination of the executive’s employment and the receipt by the executive of the shares upon exercise of the stock option. Our right of repurchase with respect to the stock options subject to any stock option agreement will lapse to the extent the shares subject to such stock option agreement become readily tradable on a nationally recognized securities exchange or market.

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The following table sets forth the amounts of compensation payable by us to our named executive officers, including cash severance, benefits and perquisites and long-term incentives. The amounts shown assume that the specified event was effective as of December 31, 2011 under their employment agreements. The actual amounts to be paid can only be determined at the time of the termination of employment or change-in-control, as applicable.

Named Executive Officer	Benefits and Payments(1)	Termination by Company Without Cause ($)			Employee Resignation for Good Reason ($)			Employee Resignation Other than for Good Reason ($)			Termination Due to Death or Disability ($)
D. Stephen Hafner	Base Salary		150,000	(2)		150,000	(2)		—			—
	Bonus		650,000	(3)		650,000	(3)		650,000	(3)		650,000	(3)
	Health and Welfare		9,807	(4)		9,807	(4)		—			—
	Continuation
Willard H. Smith	Base Salary		137,500			137,500			—			—
	Bonus		84,000	(3)		—			—			—
	Health and Welfare		10,142			—			—			—
	Continuation
Melissa H. Reiter	Base Salary		130,000	(2)		130,000	(2)		—			—
	Bonus		175,000	(3)		175,000	(5)		—			—
	Health and Welfare		3,654	(4)		—			—			—
	Continuation
Paul M. English	Base Salary		150,000	(2)		150,000	(2)		—			—
	Bonus		650,000	(3)		650,000	(3)		650,000	(3)		650,000	(3)
	Health and Welfare		9,807	(4)		9,807	(4)		—			—
	Continuation
Karen Ruzic Klein	Base Salary		130,000	(2)		—			—			—
	Bonus		275,000	(3)		—			—			—
	Health and Welfare		10,142	(4)		—			—			—
	Continuation
Robert M. Birge	Base Salary		150,000	(2)		—			—			—
	Bonus		375,000	(3)		—			—			—
	Health and Welfare		10,142	(4)		—			—			—
	Continuation

(1) In addition to the amounts described in this table, all of our employees, including each of the named executive officers, are entitled to accrued but unused vacation through the date of termination. Under our Third Amended and Restated 2005 Equity Incentive Plan, 50% of the unvested portion of the outstanding options held by each optionee as of the date of a change of control, including any unvested options held by the named executive officers, will vest and become exercisable as of such date, and the remainder of such shares shall vest and become exercisable under the circumstances described above on page 97.

(2) Amount represents six months base salary following termination.

(3) Amount represents non-equity incentive plan compensation and bonuses earned by the named executive officer in fiscal year 2011.

(4) Amount represents COBRA premiums which are payable until the earlier of six months from the date of termination, or until the named executive officer accepts other employment.

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2012 Equity Incentive Plan

The following is a summary of the material terms of the 2012 Equity Incentive Plan, which will be in effect upon completion of this offering, but does not include all of the provisions of the 2012 Equity Incentive Plan. For further information about the 2012 Equity Incentive Plan, we refer you to the complete copy of the 2012 Equity Incentive Plan, which we will file as an exhibit to our registration statement of which this prospectus is a part.

The 2012 Equity Incentive Plan provides for the grant of incentive stock option and nonstatutory stock options, stock appreciation rights, restricted stock and stock unit awards, performance units, stock grants and qualified performance-based awards, which we collectively refer to as “awards” in connection with the 2012 Equity Incentive Plan. Directors, officers and other employees of us and our subsidiaries, as well as others performing consulting or advisory services for us, are eligible for grants under the 2012 Equity Incentive Plan. The purpose of the 2012 Equity Incentive Plan is to provide incentives that will attract, retain and motivate highly competent officers, directors, employees and consultants to promote the success of our business.

Administration

Under its terms, the compensation committee of the board of directors administers the 2012 Equity Incentive Plan. The board of directors itself may exercise any of the powers and responsibilities under the 2012 Equity Incentive Plan. Subject to the terms of the 2012 Equity Incentive Plan, the plan administrator (the board or its compensation committee) will select the recipients of awards and determine, among other things, the:

• number of shares of common stock covered by the awards and the dates upon which such awards become exercisable or any restrictions lapse, as applicable;

• type of award and the exercise or purchase price and method of payment for each such award;

• vesting period for awards, risks of forfeiture and any potential acceleration of vesting or lapses in risks of forfeiture; and

• duration of awards.

All decisions, determinations and interpretations by the compensation committee, and any rules and regulations under the 2012 Equity Incentive Plan and the terms and conditions of or operation of any award, are final and binding on all participants, beneficiaries, heirs, assigns or other persons holding or claiming rights under the 2012 Equity Incentive Plan or any award.

Available Shares

The aggregate number of shares of our common stock which may be issued or used for reference purposes under the 2012 Equity Incentive Plan or with respect to which awards may be granted may not exceed                  shares, which may be either authorized and unissued shares of our common stock or shares of common stock held in or acquired for our treasury. In general, if awards under the 2012 Equity Incentive Plan are for any reason cancelled, or expire or terminate unexercised, the number of shares covered by such awards will again be available for the grant of awards under the 2012 Equity Incentive Plan. In addition, (i) shares that were subject to a stock-settled stock appreciation right and were not issued upon the net settlement or net exercise of such stock appreciation right, (ii) shares used to pay the exercise price of a stock option, (iii) shares delivered to or withheld by us to pay the withholding taxes related to an award, and (iv) shares repurchased on the open market with the proceeds of an option exercise do not count as shares issued under the 2012 Equity Incentive Plan.

The number of shares of common stock authorized under the 2012 Equity Incentive Plan also will be increased each January 1 starting in 2013 by an amount equal to the lesser of (i) 3.5% of our outstanding common stock on a fully diluted basis as of the end of our immediately preceding fiscal year, (ii) 2,000,000 shares, and (iii) any lower amount determined by our board.

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Eligibility for Participation

Members of our board of directors, as well as employees of, and consultants to, us or any of our subsidiaries and affiliates are eligible to receive awards under the 2012 Equity Incentive Plan. However, only Stephen Hafner and Paul M. English are eligible to receive grants of our Class B common stock under the 2012 Equity Incentive Plan. The selection of participants is within the sole discretion of the compensation committee.

Incentive Stock Options

Incentive stock options are intended to qualify as incentive stock options under Section 422 of the Code and will be granted pursuant to incentive stock option agreements. The plan administrator will determine the exercise price for an incentive stock option, which may not be less than 100% of the fair market value of the stock underlying the option determined on the date of grant. In addition, incentive options granted to employees who own, or are deemed to own, more than 10% of our voting stock, must have an exercise price not less than 110% of the fair market value of the stock underlying the option determined on the date of grant.

Nonstatutory Stock Options

Nonstatutory stock options are not intended to qualify as incentive stock options under Section 422 of the Code and will be granted pursuant to nonstatutory stock option agreements. The plan administrator will determine the exercise price for a nonstatutory stock option, which may not be less than the fair market value of the stock underlying the option determined on the date of grant.

Stock Appreciation Rights

A stock appreciation right, or a SAR, entitles a participant to receive a payment equal in value to the difference between the fair market value of a share of stock on the date of exercise of the SAR over the grant price of the SAR. The administrator may pay that amount in cash, in shares of our common stock, or a combination. The terms, methods of exercise, methods of settlement, form of consideration payable in settlement, and any other terms and conditions of any SAR will be determined by the administrator at the time of the grant of award and will be reflected in the award agreement. In the event a SAR is awarded together with an option, the exercise price shall equal the exercise price of the related option.

Restricted Stock and Stock Units

A restricted stock award or restricted stock unit award is the grant of shares of our common stock either currently (in the case of restricted stock) or at a future date (in the case of restricted stock units) at a price determined by the administrator (including zero), that is nontransferable and is subject to substantial risk of forfeiture until specific conditions or goals are met. Conditions may be based on continuing employment or achieving performance goals. During the period of restriction, participants holding shares of restricted stock shall, except as otherwise provided in an individual award agreement, have full voting and may have dividend rights with respect to such shares. The restrictions will lapse in accordance with a schedule or other conditions determined by the administrator.

Performance Units

A performance unit award is a contingent right to receive predetermined shares of our common stock if certain performance goals are met. The value of performance units will depend on the degree to which the specified performance goals are achieved but are generally based on the value of our common stock. The administrator may, in its discretion, pay earned performance shares in cash, or stock, or a combination of both.

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Stock Grants

A stock grant is an award of shares of common stock without restriction. Stock grants may only be made in limited circumstances, such as in lieu of other earned compensation. Stock grants are made without any forfeiture conditions.

Qualified Performance-Based Awards

Grants of performance-based awards enable us to treat other awards granted under the 2012 Equity Incentive Plan as “performance-based compensation” under Section 162(m) of the Code and preserve the deductibility of these awards for federal income tax purposes. Because Section 162(m) only applies to those employees who are “covered employees” as defined in Section 162(m), only covered employees, and those likely to become covered employees, are eligible to receive performance-based awards.

Participants under the 2012 Equity Incentive Plan are only entitled to receive payment for a performance-based award for any given performance period to the extent that pre-established performance goals set by the administrator for the period are satisfied. These pre-established performance goals must be based on one or more of the following performance criteria: pre- or after-tax net earnings, sales or revenue, operating earnings, operating cash flow, return on net assets, return on stockholders’ equity, return on assets, return on capital, stock price growth, stockholder returns, gross or net profit margin, earnings per share, price per share, and market share. These performance criteria may be measured in absolute terms or as compared to any incremental increase or as compared to results of a peer group. With regard to other awards, other than options, intended to qualify as qualified performance-based awards, the administrator has the discretion to select the length of the performance period, the type of performance-based awards to be granted, and the goals that will be used to measure the performance for the period. In determining the actual size of an individual performance-based award for a performance period, the administrator may reduce or eliminate (but not increase) the award. Generally, a participant must be employed on the date the performance-based award is paid to be eligible for a performance-based award for that period.

Transferability

Awards granted under the 2012 Equity Incentive Plan are generally nontransferable (other than by will or the laws of descent and distribution), except that the compensation committee may provide for the transferability of nonstatutory stock options at the time of grant or thereafter to certain family members.

Changes to Capital Structure

In the event of certain types of changes in our capital structure, such as a share split, the number of shares reserved under the plan and the number of shares and exercise price or strike price, if applicable, of all outstanding awards will be appropriately adjusted.

Change of Control

In the event of a reorganization or change of control event, as such terms are defined in the 2012 Equity Incentive Plan, the plan administrator shall have the discretion to provide for any or all of the following: (a) the assumption of outstanding awards or the substituting of equivalent rights by the acquiring or succeeding entity; (b) the termination of all awards immediately prior to the transaction unless exercised within a specified period; (c) the exercise of outstanding options, stock appreciation rights or the lapse in any risk of forfeiture for restricted stock and stock units (in whole or in part) upon the transaction; (d) cash payments to be made to holders; (e) the conversion of awards into the right to receive liquidation proceeds in connection with our liquidation or dissolution; or (f) any combination of the foregoing.

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Amendment and Termination

Our board of directors may at any time amend any or all of the provisions of the 2012 Equity Incentive Plan, or suspend or terminate it entirely, retroactively or otherwise. Unless otherwise required by law or specifically provided in the 2012 Equity Incentive Plan, the rights of a participant under awards granted prior to any amendment, suspension or termination may not be adversely affected without the consent of the participant. Neither our board of directors nor the administrator has the ability to reprice stock options or stock appreciation rights (other than pro rata adjustments to reflect stock splits, stock dividends or other corporate transactions, or repricings our stockholders approve), including programs under which outstanding options are surrendered or cancelled in exchange for options with a lower exercise price or greater economic value. The 2012 Equity Incentive Plan expires after ten years.

Third Amended and Restated 2005 Equity Incentive Plan

In December 2007, our board of directors and stockholders approved the Third Amended and Restated 2005 Equity Incentive Plan, which was effective for a ten-year term, to provide incentives to attract, retain and motivate highly competent officers, directors, employees and consultants to promote the success of our business. Our board of directors and stockholders amended the Third Amended and Restated 2005 Equity Incentive Plan on six occasions, each time to increase the number of shares authorized for issuance thereunder. We refer to the Third Amended and Restated 2005 Equity Incentive Plan, as amended, in this section as the 2005 Plan.

Under the 2005 Plan, the aggregate number of shares of our common stock that may be issued or with respect to which awards may be granted shall not exceed 12,000,000 shares, minus outstanding options, outstanding awards of restricted stock and shares of stock underlying exercised options under the 2004 Stock Incentive Plan, except in the event of a stock dividend, split, reclassification or other similar corporate transaction.

Employees, directors and consultants are eligible to receive options and other equity awards based on our stock under the 2005 Plan. Only employees, however, are eligible to receive incentive options. In the case of incentive options, the option price shall be not less than the fair market value of our stock underlying the option on the date the option is granted, or not less than 110% of that fair market value for a holder of 10% of our voting stock. Incentive options expire ten years after the date on which they are granted, or five years after the grant date for holders of 10% of our voting stock. Certain change-in-control transactions accelerate the vesting of options and the lapse of restrictions on other equity awards under the 2005 Plan, as more fully discussed in “—Employment Agreements and Potential Payments Upon Termination or Change-in-Control—Termination of Employment Agreements and Change-in-Control Arrangements.” Additionally, upon the filing of a registration statement with respect to shares of our common stock, the recipients of awards under the 2005 Plan become subject to lock-up periods without the requirement of formally entering into lock-up agreements.

We expect to no longer issue awards under the 2005 Plan upon completion of this offering and adopt the 2012 Equity Incentive Plan, which is discussed above. No awards outstanding under the 2005 Plan, however, will be assumed by the 2012 Equity Incentive Plan. As of January 31, 2012, options to purchase 8,426,132 shares of our common stock were outstanding, we had issued 1,553,779 shares of our common stock pursuant to the exercise of options and other equity awards and options representing 185,986 shares remained available for future issuance.

2004 Stock Incentive Plan

In May 2004 and August 2004, our board of directors and stockholders, respectively, approved the 2004 Stock Incentive Plan, effective for a ten-year term, to provide incentives to attract, retain and motivate highly competent officers, directors, employees and consultants to promote the success of our business. We refer to the 2004 Stock Incentive Plan in this section as the 2004 Plan. Under the 2004 Plan, the aggregate number of shares

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of our common stock that may be issued or with respect to which awards may be granted shall not exceed 2,180,000 shares except in the event of a stock dividend, split, reclassification or other similar corporate transaction.

Employees, directors and consultants are eligible to receive options and other equity awards based on our stock under the 2004 Plan. Only employees, however, are eligible to receive incentive options. In the case of incentive options, the option price shall be not less than the fair market value of our stock underlying the option on the date the option is granted, or not less than 110% of that fair market value for a holder of 10% of our voting stock. Incentive options expire ten years after the date on which they are granted, or five years after the grant date for holders of 10% of our voting stock. Under the 2004 Plan, we may provide financial assistance to option grantees for exercising their options, except as prohibited by applicable law. Certain change-in-control transactions accelerate the vesting of options and the lapse of restrictions on other equity awards under the 2004 Plan, as more fully discussed in “—Employment Agreements and Potential Payments Upon Termination or Change-in-Control—Termination of Employment Agreements and Change-in-Control Arrangements.” Additionally, upon the filing of a registration statement with respect to shares of our Class A common stock, the recipients of awards under the 2004 Plan become subject to lock-up periods without the requirement of formally entering into lock-up agreements.

Our board of directors discontinued grants of awards under the 2004 Plan in May 2005. As of January 31, 2012, we had issued 1,212,189 shares of our common stock pursuant to the exercise of options and other equity awards under the 2004 Plan and options representing 621,914 shares of our common stock were still outstanding.

Limitation of Liability and Indemnification of Officers and Directors

As permitted by Delaware law, our amended and restated certificate of incorporation and amended and restated by-laws that will be in effect upon completion of this offering will provide that we will indemnify our directors and officers to the fullest extent permitted by Delaware law. Upon completion of this offering, we expect to have in place directors’ and officers’ liability insurance that insures our directors and officers against the costs of defense, settlement or payment of a judgment under certain circumstances. See “Certain Relationships and Related Party Transactions—Indemnification of Officers and Directors” for more information.

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CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS

Related Party Transactions

We describe below transactions since January 1, 2008 to which we were a party or will be a party, in which:

• the amounts involved exceeded or will exceed $120,000; and

• any of our directors, executive officers, holders of more than 5% of our currently outstanding common stock, which will automatically be converted into Class B common stock upon completion of this offering, or any member of their immediate family had or will have a direct or indirect material interest.

Loans to Daniel Stephen Hafner

On July 3, 2008, we loaned $550,000 to Mr. Hafner, our Chief Executive Officer and one of our directors, evidenced by a secured promissory note dated the same day. The note accrued interest at a rate of 3.2% per annum and was secured by a pledge of 75,000 shares of our common stock. On January 22, 2009, we loaned an additional $1,000,000 to Mr. Hafner and substituted his obligations under the earlier note with a secured promissory note and novation dated the same day. The new note accrued interest at a rate of 2.06% per annum and was secured by a pledge of 301,904 shares of our common stock.

As of March 24, 2010, Mr. Hafner repaid $1,550,000 of principal and $45,818 as interest in full satisfaction of his obligations under the secured promissory note and novation.

Loans to Paul M. English

On July 3, 2008, we loaned $550,000 to Mr. English, our Chief Technology Officer and one of our directors, evidenced by a secured promissory note dated the same day. The note accrued interest at a rate of 3.2% per annum and was secured by a pledge of 75,000 shares of our common stock. On March 20, 2009, we loaned an additional $1,500,000 to Mr. English and substituted his obligations under the earlier note with a secured promissory note and novation dated the same day. The new note accrued interest at a rate of 2.06% per annum and was secured by a pledge of 399,210 shares of our common stock.

As of March 26, 2010, Mr. English repaid $2,050,000 of principal and $53,175 as interest in full satisfaction of his obligations under the secured promissory note and novation.

Sale of Travelpost.com

On March 5, 2010, we sold certain of our assets related to the website travelpost.com and its travel information business to The New Travelco, Inc., a Delaware corporation, which subsequently changed its name to TravelPost, Inc. These assets consisted primarily of TravelPost-specific web content, software components, customer information, web domain names, trademarks and trademark applications, contracts and goodwill associated with TravelPost. Mr. Slyngstad, one of our directors at the time, was the Chief Executive Officer and is a director of TravelPost, Inc., and General Catalyst Group V, L.P. and GC Entrepreneurs Fund V, L.P., both of which are affiliated with General Catalyst Partners, of which Joel E. Cutler, one of our directors, is managing director and cofounder, are stockholders of TravelPost, Inc. On March 5, 2010, we entered into the following agreements with The New Travelco, Inc. in connection with the transaction:

• Asset Purchase Agreement, which provides for the sale to The New Travelco, Inc. of certain assets in exchange for $3.6 million in cash, 800,000 shares of The New Travelco, Inc. common stock and the assumption by The New Travelco, Inc. of certain of our obligations. The purchase price was established through a combination of third-party appraisal efforts and negotiations between us and The New Travelco, Inc.

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• Commercial Agreement which was subsequently amended in March 2011, pursuant to which we granted to The New Travelco, Inc. a three-year license to reproduce and publicly display hotel reviews and hotel-related information in exchange for a monthly license fee of $10,000 for the remaining term of the license and 1,000,000 shares of Series A preferred stock of TravelPost, Inc.

• Common Stock Purchase Agreement, providing for the transfer to us of 800,000 shares of The New Travelco, Inc. common stock referred to above and under which we agreed to a lock-up period of 180 days following The New Travelco, Inc.’s first firm commitment underwritten public offering of its common stock.

• Patent License Agreement, pursuant to which we granted The New Travelco, Inc. a royalty-free and perpetual license to use certain processes for the operation of the travelpost.com website and associated domain names.

• Software License Agreement, pursuant to which we granted The New Travelco, Inc. a royalty-free and perpetual license to use certain computer programs in connection with the operation of the travelpost.com website and related domain names.

• Right of First Refusal and Co-Sale Agreement, pursuant to which we agreed to certain preemptive rights in favor of The New Travelco, Inc. with respect to its shares of common stock held by us. Mr. Slyngstad, General Catalyst Group V, L.P., GC Entrepreneurs Fund V, L.P. and certain other stockholders of The New Travelco, Inc. were additional parties to the agreement.

• Voting Agreement, under which we agreed to vote shares of The New Travelco, Inc.’s capital stock held by us in favor of the election of certain individuals as directors of The New Travelco, Inc. in accordance with the provisions of the agreement. Mr. Slyngstad, General Catalyst Group V, L.P., GC Entrepreneurs Fund V, L.P. and certain other stockholders of The New Travelco, Inc. were additional parties to the agreement.

Stockholders’ Agreement

On May 6, 2010, in connection with our acquisition of swoodoo, we entered into a Stockholders’ Agreement with certain holders of our convertible preferred stock and our common stock, including funds affiliated with General Catalyst Partners, funds affiliated with Sequoia Capital, of which Michael Moritz, one of our directors, is a partner, funds affiliated with Accel Partners, of which Hendrik W. Nelis, another of our directors, is a partner, Oak Investment Partners, one of our stockholders, Mr. Hafner, Mr. English and Dr. Christian W. Saller, our Managing Director for Europe. The requisite stockholder parties to this agreement have agreed that this agreement will terminate upon the consummation of this offering. Among other things, the agreement, as amended to date, provides for the following:

• it gives us and certain of our stockholders the right of first refusal with respect to a sale of any of the shares of our common stock issued to Dr. Saller and other former swoodoo stockholders in connection with the acquisition, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering;

• it obligates Dr. Saller and other holders of the shares of our common stock issued in connection with the acquisition, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, to vote their shares for the election of the members of our board of directors consistent with the terms of our Sixth Amended and Restated Stock Restriction and Co-Sale Agreement; and

• it provides that, in the event of an approved sale of us, Dr. Saller and other holders of the shares of our common stock issued in connection with the acquisition, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, shall be required to vote their shares in favor of the sale.

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Stock Restriction and Co-Sale Agreement

On December 22, 2011, we entered into the Sixth Amended and Restated Stock Restriction and Co-Sale Agreement with certain holders of our convertible preferred stock and our common stock, including America Online, Inc., certain funds affiliated with General Catalyst Partners, Sequoia Capital and Accel Partners, respectively, Oak Investment Partners, Mr. Slyngstad, Mr. Hafner, trusts of which Mr. Hafner is a trustee, Mr. English and trusts of which Mr. English is a trustee. The requisite stockholder parties to this agreement have agreed that this agreement will terminate upon the consummation of this offering. Among other things, the agreement, as amended to date, provides for the following:

• it gives us and the preferred stockholders party to the agreement a right of first refusal with respect to proposed sales by certain holders of shares of KAYAK common stock listed in the agreement, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, to third parties;

• it establishes the composition of our board of directors;

• It provides that, in the event of an approved sale of our company, the parties to the agreement shall also be obligated to vote in favor of the sale; and

• it gives Oak Investment Partners the right to designate a board observer.

Investor Rights Agreement

On March 22, 2010, we entered into the Sixth Amended and Restated Investor Rights Agreement with certain of our investors referred to therein and our founders group, consisting of Mr. Hafner and trusts of which Mr. Hafner is a trustee and Mr. English and trusts of which Mr. English is a trustee. The investors include funds affiliated with General Catalyst Partners, funds affiliated with Sequoia Capital, funds affiliated with Accel Partners, Oak Investment Partners, Messrs. Slyngstad, Hafner and English. Among other things, the agreement, as amended to date, provides for the following:

• it provides certain holders of shares of our convertible preferred stock and common stock, which shares of common stock will be automatically converted into shares of our Class B common stock upon completion of this offering, with certain demand, “piggyback” and short-form registration rights, subject to lock-up arrangements;

• it provides for indemnification for certain liabilities in connection with a registration of our securities; and

• it establishes certain restrictions with respect to the transfer and issuance of our capital stock, including a right of first refusal in favor of certain investors and our founders group with respect to the issuance of certain securities by us, and it contains other restrictions, including limitations on our ability to incur debt, except for indebtedness under certain specified loan arrangements; however, these restrictions will automatically terminate upon the completion of this offering, so long as the offering is completed pursuant to a registration statement which becomes effective prior to December 31, 2012.

Election and Amendment Agreement

On April 19, 2012, we entered into the Election and Amendment Agreement with the holders of a majority of our capital stock. In addition to providing for the concurrent private placements which are described in the section of this prospectus titled “Concurrent Private Placements,” the Election and Amendment Agreement amends our Stockholders’ Agreement, Stock Restriction and Co-Sale Agreement and Investor Rights Agreement, and included an election by such stockholders under, and consent to an amendment to, our certificate of incorporation. The effect of such election and amendments is, among other things, to cause all shares of our convertible preferred stock to convert into shares of Class B common stock concurrently with the closing of any initial public offering that is completed pursuant to a registration statement which becomes effective prior to

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December 31, 2012, regardless of the initial public offering price in such offering. Pursuant to such election and amendments, the stockholders have also waived certain potential preemptive and anti-dilution related rights which they may have had upon completion of this offering and the concurrent private placements, and are causing the amended Stockholders’ Agreement and Stock Restriction and Co-Sale Agreement, and certain provisions of the amended Investor Rights Agreement, to automatically terminate upon the completion of this offering.

Services Agreement with ITA Software, Inc.

On March 3, 2005, we entered into a Services Agreement with ITA, of which Mr. Cutler was a director and funds affiliated with General Catalyst Partners were 10% stockholders, for the licensing to us of airline faring engine software. The agreement was subsequently amended on July 18, 2007, March 11, 2008 and January 1, 2009. We paid ITA an initial payment of $166,666 followed by a monthly service fee based on the number of queries performed, subject to a minimum of $83,333 per month, a software maintenance and operation fee of $225 per hour and a hardware fee per month of $1,450 per dual processor server used.

On March 11, 2008, in addition to our arrangement with ITA, we agreed to assume payment obligations of SideStep to ITA following our acquisition of SideStep. On January 1, 2009, we agreed to amend the fee schedule as follows: to increase the monthly service fee to a minimum of $500,000 for the period until January 1, 2010, and a minimum of $583,333 per month thereafter until our aggregate payments for 2012 equal certain agreed-upon amounts, following which we would cease such monthly minimum payments until January 1, 2013, whereupon we have agreed to pay a minimum monthly fee to be calculated based upon the number of queries performed in 2012. For the period from January 1, 2012 through December 31, 2012, we have an estimated minimum commitment of approximately $7.0 million related to this agreement. We are unable to estimate our calendar year 2013 minimum commitment at this time.

Legal Services

Katten Muchin Rosenman LLP, a law firm of which our General Counsel’s spouse is a corporate partner, billed us an aggregate of $6,520 for legal services provided to us by various employment, bankruptcy & antitrust attorneys during the three months ended March 31, 2012 and an aggregate amount of $849,920 for legal services provided to us during the period commencing on January 1, 2009 and ending on March 31, 2012.

Indemnification of Officers and Directors

Our amended and restated certificate of incorporation and amended and restated by-laws that will be in effect upon completion of this offering will provide that we will indemnify our directors and officers to the fullest extent permitted by Delaware law. We have purchased directors’ and officers’ liability insurance that insures against the costs of defense, settlement or payment of a judgment under certain circumstances. We have also purchased employed lawyer’s insurance, under which our employees who are attorneys, including Ms. Klein, our General Counsel and Secretary, are insured against claims of legal malpractice in certain situations. In addition, our amended and restated certificate of incorporation provides that our directors will not be liable for monetary damages for breach of fiduciary duty.

In addition, on April 15, 2008, our board of directors approved a form of indemnification agreement to be entered into with each of our nonemployee directors. We subsequently entered into such an agreement with each of Messrs. Jones, Cutler, Moritz, Slyngstad and Nelis. The indemnification agreements provide the directors with contractual rights to indemnification, expense advancement and reimbursement, to the fullest extent permitted under Delaware law. We also expect our directors and executive officers to enter into a new form of indemnification agreement prior to completion of this offering. We may also enter into indemnification agreements with any new directors or certain of our executive officers that may be broader in scope than the

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specific indemnification provisions contained in the indemnification agreements described above or under Delaware law.

There is no pending litigation or proceeding naming any of our directors or officers to which indemnification is being sought, and we are not aware of any pending or threatened litigation that may result in claims for indemnification by any director or officer.

Procedures for Approval of Related Party Transactions

We do not currently have in effect a formal, written policy or procedure for the review and approval of related party transactions. However, all related party transactions are currently reviewed and approved by a disinterested majority of our board of directors.

Our board of directors has adopted a written policy, to be effective upon the completion of this offering, for the review of any transaction, arrangement or relationship in which we are a participant, the amount involved exceeds $100,000 and one of our executive officers, directors, director nominees or 5% stockholders (or their immediate family members), each of whom we refer to as a related party, has a direct or indirect interest.

If a related party proposes to enter into such a transaction, arrangement or relationship, which we refer to as a related party transaction, the related party must report the proposed related party transaction to the chairperson of our nominating and governance committee. Additionally, under the policy, we will solicit this information from directors, executive officers and 5% stockholders via annual questionnaires. The policy calls for the proposed related party transaction to be reviewed and, if deemed appropriate, approved by the nominating and governance committee. Whenever practicable, the reporting, review and approval will occur prior to entering into the transaction. If advance review and approval is not practicable, the nominating and governance committee will review and, in its discretion, may ratify the related party transaction. Any related party transactions that are ongoing in nature will be reviewed annually and the nominating and governance committee may establish guidelines for our management to follow its ongoing dealings with the related party.

A related party transaction reviewed under the policy will be considered approved or ratified if it is authorized by the nominating and governance committee after full disclosure of the related party’s interest in the transaction. The written policy also provides for the standing pre-approval of certain related party transactions, such as the employment compensation of executive officers, director compensation and certain charitable contributions, among other things. The policy includes a nepotism policy under which no immediate family member of a director or executive officer shall be hired until the employment arrangement is approved by the nominating and governance committee or, if it is not practicable for us to wait until the next nominating and governance committee meeting, by the chairperson of such committee.

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PRINCIPAL STOCKHOLDERS

The following table sets forth certain information regarding the beneficial ownership of our common stock as of March 31, 2012 with respect to:

• each person known by us to beneficially own 5% or more of the outstanding shares of our common stock;

• each member of our board of directors;

• each named executive officer; and

• the members of our board of directors and our executive officers as a group.

Unless otherwise noted below, the address of each beneficial owner listed in the table below is c/o KAYAK Software Corporation, 55 North Water Street, Suite 1, Norwalk, CT 06854.

We have determined beneficial ownership in accordance with the rules of the SEC. Except as indicated by the footnotes below, we believe, based on the information furnished to us, that the persons and entities named in the table below have sole voting and investment power with respect to all shares of common stock that he, she or it beneficially owns.

Applicable percentage ownership and voting power prior to the offering is based on 33,805,623 shares of common stock outstanding on March 31, 2012, assuming for purposes of this table that all outstanding shares of our convertible preferred stock have been converted to common stock. For purposes of the table below, with respect to applicable percentage ownership and voting power after this offering we have assumed that all outstanding shares of our common stock and our convertible preferred stock have been converted to Class B common stock, that 33,805,623 shares of Class B common stock will be outstanding upon completion of the offering and, based on an assumed initial public offering price of $             per share, the midpoint of the initial public offering price range set forth on the cover of this prospectus, that                      shares of Class A common stock are issued pursuant to the automatic adjustment. None of the stockholders included in the table below beneficially owned any shares of Class A common stock prior to this offering. In computing the number of shares of common stock beneficially owned by a person and the percentage ownership of that person, we deemed outstanding shares of common stock subject to options held by that person, including shares issuable upon exercise of the private placement purchase rights, that are currently exercisable or exercisable within 60 days of March 31, 2012. We did not deem these shares outstanding, however, for the purpose of computing the percentage ownership of any other person.

Name and Address of     Beneficial Owner	Shares Beneficially Owned Prior to this Offering and the Concurrent Private Placements									Shares Beneficially Owned After this Offering and the Concurrent Private Placements Assuming No Exercise of Over- Allotment Option			Shares Beneficially Owned After this Offering and the Concurrent Private Placements Assuming Full Exercise of Over- Allotment Option
	Number			Percent			% Total Voting Power**			Number	Percent	% Total Voting Power**	Number	Percent	% Total Voting Power**
5% Stockholders:
General Catalyst Partners		10,146,960	(1)		30.02	%		30.02	%
Sequoia Capital		6,000,797	(2)		17.75	%		17.75	%
Accel Funds		4,797,286	(3)		14.19	%		14.19	%
Oak Investment Partners		3,585,272	(4)		10.61	%		10.61	%
Directors and Named Executive Officers:
Daniel Stephen Hafner		2,346,198	(5)(6)(7)		6.92	%		6.92	%
Paul M. English		3,033,328	(5)(8)(9)		8.94	%		8.94	%
Joel E. Cutler		10,146,960	(1)		30.02	%		30.02	%
Michael Moritz		6,000,797	(2)		17.75	%		17.75	%
Hendrik W. Nelis		4,797,286	(3)		14.19	%		14.19	%

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Name and Address of     Beneficial Owner

Shares Beneficially Owned Prior to this Offering and the Concurrent Private Placements

Shares Beneficially Owned After this Offering and the Concurrent Private Placements Assuming No Exercise of Over- Allotment Option

Shares Beneficially Owned After this Offering and the Concurrent Private Placements Assuming Full Exercise of Over- Allotment Option

Number

Percent

% Total Voting Power**

Number

Percent

% Total Voting Power**

Number

Percent

% Total Voting Power**

Terrell B. Jones

284,000

(5)

*

*

Brian H. Sharples

—

—

—

Gregory S. Stanger

—

—

—

Willard H. Smith

50,000

*

*

Melissa H. Reiter

89,581

(5)

*

*

Karen Ruzic Klein

170,300

(5)

*

*

Robert M. Birge

183,384

(5)

*

*

All executive officers and directors as a group (17 individuals)

28,467,508

79.07

%

79.07

%

 * Indicates ownership of less than one percent.

** Percentage total voting power represents voting power with respect to all shares of our Class A and Class B common stock, voting as a single class. Each holder of Class B common stock shall be entitled to ten votes per share of Class B common stock and each holder of Class A common stock shall be entitled to one vote per share of Class A common stock on all matters submitted to our stockholders for a vote. The Class A common stock and Class B common stock vote together as a single class on all matters submitted to a vote of our stockholders, except as may otherwise be required by law. The Class B common stock is convertible at any time by the holder into shares of Class A common stock on a share-for-share basis.

(1) Consists of 10,146,960 shares of our common stock, representing 490,231 shares of outstanding common stock and 9,656,729 shares of common stock pursuant to the conversion of:

• 5,000,000 shares of Series A convertible preferred stock;

• 624,445 shares of Series A-1 convertible preferred stock;

• 1,229,508 shares of Series B convertible preferred stock;

• 705,309 shares of Series B-1 convertible preferred stock;

• 167,617 shares of Series C convertible preferred stock; and

• 1,929,850 shares of our Series D convertible preferred stock.

Such common stock is held by General Catalyst Partners as follows:

• 155,863 shares held by GC Entrepreneurs Fund II, L.P.

• 149,701 shares held by GC Entrepreneurs Fund III, L.P.

• 32,150 shares held by GC Entrepreneurs Fund V, LP

• 4,131,405 shares held by General Catalyst Group II, L.P.

• 4,137,570 shares held by General Catalyst Group III, L.P.

• 1,026,847 shares held by General Catalyst Group V Supplemental L.P.; and

• 513,424 shares held by General Catalyst Group V, L.P.

Each of David Fialkow, David Orfao, John Simon and Joel Cutler, our director, is a Managing Director of General Catalyst GP II, LLC, General Catalyst GP III, LLC and General Catalyst GP V, LLC and may be deemed to share voting and dispositive power over the shares held of record by General Catalyst Group II, L.P., General Catalyst Group III, L.P., General Catalyst Group V, L.P., General Catalyst Group V Supplemental, L.P., GC Entrepreneurs Fund II, L.P., GC Entrepreneurs Fund III, L.P., and GC Entrepreneurs Fund V, L.P. Each of the Managing Directors disclaims beneficial ownership of any such shares except to the extent of his proportionate pecuniary interest therein. The address for Mr. Cutler and General Catalyst Partners is 20 Cambridge Road, 4th Floor, Cambridge, MA 02138.

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(2) Consists of 6,000,797 shares of our common stock, representing 279,470 shares of outstanding common stock and 5,721,327 shares of common stock pursuant to the conversion of:

• 243,281 shares of Series A-1 convertible preferred stock;

• 3,047,042 shares of Series B convertible preferred stock;

• 333,539 shares of Series B-1 convertible preferred stock;

• 167,617 shares of Series C convertible preferred stock; and

• 1,929,848 shares of Series D convertible preferred stock.

Such common stock is held by Sequoia Capital as follows:

• 2,269,059 shares held by Sequoia Capital Growth Fund III

• 111,677 shares held by Sequoia Capital Growth III Principals Fund

• 22,338 shares held by Sequoia Capital Growth Partners III

• 3,154,842 shares held by Sequoia Capital XI

• 343,224 shares held by Sequoia Capital XI Principals Fund; and

• 99,657 shares held by Sequoia Technology Partners XI

SCGF III Management, LLC is the managing member of Sequoia Capital Growth Fund III, Sequoia Capital Growth Partners III and Sequoia Capital Growth Principals Fund III and has sole voting and investment power. SCXI Management, LLC is the managing member of Sequoia Capital XI, Sequoia Capital XI Principals Fund and Sequoia Technology Partners XI and has sole voting and investment power. Voting and investment power over the shares beneficially owned by SCGF III Management, LLC is shared by Michael Moritz, our director, Roelof Botha, James Goetz, Douglas Leone, Scott Carter, and Mike Goguen, its managing members. Voting and investment power over the shares beneficially owned by SCGF III Management, LLC is shared by Michael Moritz, our director, and Douglas Leone, and Mike Goguen, its managing members. The managing members disclaim beneficial ownership of such shares except to the extent of their respective proportionate pecuniary interests therein. The address for Mr. Moritz and Sequoia Capital is 3000 Sand Hill Road, 4-250, Menlo Park, CA 94025.

(3) Consists of 4,797,286 shares of our common stock, representing 217,136 shares of outstanding common stock and 4,580,150 shares of common stock pursuant to the conversion of:

• 400,000 shares of Series A convertible preferred stock;

• 177,747 shares of Series A-1 convertible preferred stock;

• 3,519,946 shares of Series C convertible preferred stock; and

• 482,457 shares of Series D convertible preferred stock.

Such common stock is held by Accel Funds as follows:

• 4,698,942 shares held by Accel London II, L.P.; and

• 98,344 shares held by Accel London Investors 2006 L.P.

(Accel London II, L.P. and Accel London Investors 2006 L.P. being collectively the “Accel Funds”)

Accel London II Associates L.L.C. is the general partner of Accel London II Associates L.P., which is the general partner of Accel London II L.P. and has the sole voting and investment power. Accel London II Associates L.L.C. is the general partner of Accel London Investors 2006 L.P. and has the sole voting and investment power. Voting and investment power over the shares beneficially owned by Accel London II Associates L.L.C. is shared by the managers, Jonathan Biggs, Kevin Comolli, Bruce Golden and Hendrik W. Nelis. The general partner and managers disclaim beneficial ownership of the shares owned by the Accel Funds except to the extent of their proportionate pecuniary interest therein.

The address for Mr. Nelis is 16 St. James’s Street, London SW1A 1ER, United Kingdom. The address for the Accel Funds is 428 University Avenue, Palo Alto, CA 94301.

(4) Consists of 3,585,272 shares of our common stock, representing 717,797 shares of outstanding common stock and 2,267,475 shares of common stock pursuant to the conversion of:

• 375,000 shares of Series A convertible preferred stock;

• 96,417 shares of Series A-1 convertible preferred stock;

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• 225,000 shares of Series B-1 convertible preferred stock; and

• 2,171,058 shares of Series D convertible preferred stock.

Oak Investment Partners XII, LP, a Delaware limited partnership, is controlled by Oak Associates XII, LLC, its General Partner. Voting and dispositive power over the shares held of record by Oak Investment Partners XII, LP may be deemed to be held by Bandel L. Carano, Edward F. Glassmeyer, Frederic W. Harman, Ann H. Lamont and Iftikar A. Ahmed, managing members of Oak Associates XII, LLC. The managing members disclaim beneficial ownership of the shares held by Oak Investment Partners XII, LP except to the extent of their respective proportionate pecuniary interests therein. The principal address for Oak Investment Partners XII, LP is One Gorham Island, Westport, Connecticut 06880.

(5) Includes the following number of shares of common stock which a director or executive officer has the right to acquire upon the exercise of stock options that were exercisable as of March 31, 2012, or that will become exercisable within 60 days after that date:

Name	Number of Shares
Daniel Stephen Hafner		116,666
Paul M. English		116,666
Terrell B. Jones		274,000
Melissa H. Reiter		89,581
Karen Ruzic Klein		166,666
Robert M. Birge		162,498
Willard H. Smith		50,000

For purposes of computing the percentage of outstanding shares of common stock held by each person named above, we have given effect to such person’s options, each as noted above, and as if they were fully exercised.

(6) Includes 1,627,265 shares of our common stock beneficially owned by Mr. Hafner as follows:

• 398,591 shares of outstanding common stock, and 603,674 shares of common stock pursuant to the conversion of: 175,000 shares of Series A convertible preferred stock, 161,390 shares of Series B convertible preferred stock and 267,284 shares of Series B-1 convertible preferred stock held directly by Mr. Hafner;

• 500,000 shares of common stock held by the DS Hafner Trust, which beneficial ownership Mr. Hafner disclaims;

• 100,000 shares of common stock held by Daniel Stephen Hafner, as trustee for the JM Hafner Trust, which beneficial ownership Mr. Hafner disclaims; and

• 25,000 shares of common stock held by Daniel Stephen Hafner as trustee for the McKane 2007 Grandchildren Trust, which beneficial ownership Mr. Hafner disclaims.

(7) Includes 602,267 shares over which Mr. Hafner has limited voting power pursuant to a voting agreement and proxy dated April 13, 2011. These shares are composed of 398,591 shares of outstanding common stock and 203,676 shares of common stock pursuant to the conversion of 161,391 shares of Series B convertible preferred stock and 42,285 shares of Series B-1 convertible preferred stock. Mr. Hafner disclaims beneficial ownership of such shares.

(8) Includes 1,894,534 shares beneficially owned by Mr. English as follows:

• 198,015 shares of outstanding common stock, and 803,675 shares of common stock pursuant to the conversion of: 375,000 shares of Series A convertible preferred stock, 161,391 shares of Series B convertible preferred stock and 267,284 shares of Series B-1 convertible preferred stock held directly by Mr. English;

• 100,000 shares of common stock held by Paul M. English, as trustee for The Paul M. English 2007 Irrevocable Family Trust, which beneficial ownership Mr. English disclaims;

• 315,880 shares of common stock held by Paul M. English as trustee for The Paul M. English 2009 Charitable Remainder Unitrust I, which beneficial ownership Mr. English disclaims; and

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• 315,880 shares of common stock held by Paul M. English as trustee for The Paul M. English 2009 Charitable Remainder Unitrust II, which beneficial ownership Mr. English disclaims.

• 161,084 shares of common stock held by a trust for the benefit of Mr. English’s minor child living in Mr. English’s household; Mr. English is not the trustee or beneficiary of such trust and disclaims beneficial ownership of such shares.

(9) Includes 1,022,128 shares over which Mr. English has sole voting power pursuant to a proxy dated November 5, 2010. These shares are composed of 418,453 shares of outstanding common stock, and 603,675 shares of common stock pursuant to the conversion of 175,000 shares of Series A convertible preferred stock, 161,390 shares of Series B convertible preferred stock and 267,285 shares of Series B-1 convertible preferred stock. Mr. English disclaims beneficial ownership of such shares.

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DESCRIPTION OF CAPITAL STOCK

General

The following is a summary of our capital stock and provisions of our amended and restated certificate of incorporation and amended and restated by-laws, as each will be in effect upon the completion of this offering, and certain provisions of Delaware law. This summary does not purport to be complete and is qualified in its entirety by the provisions of our amended and restated certificate of incorporation and amended and restated by-laws, copies of which will be filed as exhibits to this registration statement of which this prospectus is a part. References in this section to “we,” “us” and “our” refer to KAYAK Software Corporation and not to any of its subsidiaries.

Authorized Capitalization

Prior to this offering, we had one class of common stock outstanding. In accordance with the terms of our amended and restated certificate of incorporation, which will become effective prior to the consummation of this offering, each share of our outstanding common stock will be reclassified automatically upon closing of the offering and without any action on the part of the holders of those shares into              shares of our Class B common stock. In addition, immediately prior to the consummation of this offering, we will increase our total authorized number of shares of capital stock, and amend our certificate of incorporation and By-laws as described below. Except where otherwise noted, the description of the terms of our charter documents below reflects the terms of those documents as they will be following the reclassification.

Upon completion of this offering, our authorized capital stock will consist of              shares of Class A common stock, $0.001 par value per share,              shares of Class B common stock, $0.001 per value per share, and              shares of undesignated preferred stock, $0.001 par value per share. Immediately following the completion of this offering, based on an assumed initial public offering price of $             per share, the midpoint of the price range set forth on the cover of this prospectus, there are expected to be              shares of Class A common stock outstanding, including                      shares of our Class A common stock issuable pursuant to the automatic adjustment described under “Concurrent Private Placements,”              shares of Class B common stock outstanding, and no shares of preferred stock outstanding.

As of                     , and assuming the conversion of all outstanding convertible preferred stock into Class B common stock and the conversion of all outstanding warrants into warrants for Class B common stock, which will occur immediately prior to completion of this offering, there were outstanding:

• zero shares of our Class A common stock;

•             shares of our Class B common stock held by approximately             stockholders of record;

•             shares of our Class B common stock issuable upon exercise of outstanding stock options; and

•             shares of our Class B common stock issuable upon exercise of the warrants described above.

Common Stock

Voting Rights

Holders of our Class A common stock are entitled to one vote per share and holders of our Class B common stock are entitled to ten votes per share. Holders of shares of Class A common stock and Class B common stock will vote together as a single class on all matters (including the election of directors) submitted to a vote of stockholders, unless otherwise required by law. Delaware law could require either our Class A common stock or Class B common stock to vote separately as a single class in the following circumstances:

• If we amended our certificate of incorporation to increase the authorized shares of a class of stock, or to increase or decrease the par value of a class of stock, then that class would be required to vote separately to approve the proposed amendment.

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• If we amended our certificate of incorporation in a manner that altered or changed the powers, preferences or special rights of a class of stock in a manner that affects them adversely then that class would be required to vote separately to approve the proposed amendment.

An election of directors by our stockholders shall be determined by a plurality of the votes cast by the stockholders entitled to vote on the election, meaning directors receiving the highest number of affirmative votes cast are elected. There are no cumulative voting rights for the election of directors, which means that the holders of a majority of the shares of our common stock voted will be entitled to elect all of our directors then standing for election.

Conversion

Our Class A common stock is not convertible into any other shares of our capital stock.

Each share of Class B common stock is convertible at any time at the option of the holder into one share of Class A common stock. In addition, each share of Class B common stock shall convert automatically into one share of Class A common stock upon any transfer, whether or not for value, except for certain transfers described in our certificate of incorporation, including the following:

• Transfers between Daniel Stephen Hafner and Paul English, our founders.

• Transfers for certain tax and estate planning purposes, including to trusts, corporations and partnerships controlled by a holder of Class B common stock.

In addition, partnerships or limited liability companies that hold more than 5% of the total outstanding shares of Class B common stock as of the closing of the offering may distribute their Class B common stock to their respective partners or members (who may further distribute the Class B common stock to their respective partners or members) without triggering a conversion to Class A common stock. Such distributions must be conducted in accordance with the ownership interests of such partners or members and the terms of any agreements binding the partnership or limited liability company.

The death of any holder of Class B common stock who is a natural person will result in the conversion of his or her shares of Class B common stock to Class A common stock. However, either of our founders may transfer voting control of shares of Class B common stock to the other founder contingent or effective upon their death without triggering a conversion to Class A common stock, provided that the shares of Class B common stock so transferred shall convert to Class A common stock nine months after the death of the transferring founder.

All authorized shares of Class B common stock shall automatically convert to Class A common stock on the seven-year anniversary date of completion of this offering. Once transferred and converted into Class A common stock, the Class B common stock shall not be reissued. No class of common stock may be subdivided or combined unless the other class of common stock concurrently is subdivided or combined in the same proportion and in the same manner.

Dividends

Holders of our Class A common stock and Class B common stock are entitled to receive proportionately any dividends of any of our funds legally available when, as and if declared by the board of directors, subject to any preferential dividend rights of any then outstanding shares of preferred stock.

Liquidation

Upon the dissolution, liquidation or winding up of KAYAK, holders of our Class A common stock and Class B common stock would be entitled to receive proportionately all assets available for distribution to

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stockholders after the payment of all of our debts and other liabilities and the satisfaction of any liquidation preference granted to the holders of any then outstanding shares of preferred stock.

Rights and Preferences

Holders of our Class A common stock and Class B common stock will have no preemptive, subscription, conversion or other rights, and there are no redemption or sinking fund provisions applicable to our Class A common stock or Class B common stock. The rights, preferences and privileges of holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that we may designate and issue in the future.

Preferred Stock

Under the terms of our amended and restated certificate of incorporation that will be in effect upon completion of this offering, our board of directors will have the authority, without further action by our stockholders, to issue up to              shares of preferred stock in one or more series and to fix the rights, preferences, privileges and restrictions thereof, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences that could dilute the voting power or rights of holders of our Class A common stock and Class B common stock.

The purpose of authorizing our board of directors to issue preferred stock and determine its rights and preferences is to eliminate delays associated with a stockholder vote on specific issuances. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions, future financings and other corporate purposes, could make it more difficult for a third party to acquire, or could discourage a third party from seeking to acquire, a majority of our outstanding voting stock. Upon completion of this offering, there will be no shares of preferred stock outstanding, and we have no present plans to issue any shares of preferred stock.

Warrants and Other Purchase Rights

Upon completion of this offering, all outstanding warrants to purchase an aggregate 41,904 shares of our Series C convertible preferred stock and an aggregate 62,000 shares of our Series D convertible preferred stock will convert to warrants to purchase an aggregate 103,904 shares of our Class B common stock. These warrants are exercisable at the holder’s election. Subject to certain acceleration provisions, the warrants related to the Series C convertible preferred stock and the Series D convertible preferred stock expire on November 22, 2016 and December 31, 2017, respectively.

If at the time of expiration, the fair market value of the shares of our Class A common stock issuable upon exercise of the warrants is greater than the warrant exercise price, the warrants will automatically convert into a number of shares of our Class B common stock determined by dividing the fair market value of our Class A common stock divided by the fair market value minus the per share warrant exercise price. The warrant is also subject to adjustment for stock dividends and stock splits.

In addition, as further described in the section of this prospectus titled “Concurrent Private Placements,” if our initial public offering price is less than $31.09 per share, certain existing stockholders have purchase rights to acquire from us, at the initial public offering price, up to an aggregate of $9.2 million of our Class A common stock. We refer to these rights as the private placement purchase rights. These rights must be exercised, if at all, within five business days of the date on which we consummate the initial public offering. We will receive the full proceeds of any shares purchased in this private placement, and will not pay any underwriting discounts or commissions on these shares.

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Registration Rights

Pursuant to the terms of an Investor Rights Agreement between us and certain holders of our stock, certain holders of our stock are entitled to require us to register any or all of their shares under the Securities Act at our expense, subject to certain limitations. The stockholders who are a party to the Investor Rights Agreement will hold an aggregate of approximately              shares, or approximately     %, of our common stock outstanding upon completion of this offering (assuming no exercise of the underwriters’ over-allotment option). See “Certain Relationships and Related Party Transactions—Related Party Transactions—Investor Rights Agreement” for more information.

Antitakeover Provisions

Certain provisions of Delaware law and our amended and restated certificate of incorporation and amended and restated by-laws that will be in effect upon consummation of the offering could make the acquisition of KAYAK more difficult. These provisions, summarized below, may have the effect of deterring hostile takeovers, delaying or preventing changes in control of our management or our company, such as a merger, reorganization or tender offer. These provisions are intended to enhance the likelihood of continued stability in the composition of our board of directors and its policies and to discourage certain types of transactions that may involve an actual or threatened acquisition of us. These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal. The provisions also are intended to discourage certain tactics that may be used in proxy fights. However, such provisions could have the effect of discouraging others from making tender offers for our shares and, as a consequence, they also may inhibit fluctuations in the market price of our shares that could result from actual or rumored takeover attempts. Such provisions may also have the effect of preventing changes in our management.

Amended and Restated Certificate of Incorporation and Amended and Restated By-laws to be in Effect Upon the Completion of this Offering

Stockholder Meetings. Under our amended and restated certificate of incorporation and amended and restated by-laws to be in effect upon completion of this offering, only a majority of our board of directors, the chairperson of the board of directors or the Chief Executive Officer may call special meetings of stockholders.

Advance Notice of Stockholder Nominations and Proposals. Our amended and restated by-laws will establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of stockholders, including proposed nominations of candidates for election to our board of directors. Stockholders at an annual meeting will only be able to consider proposals or nominations specified in the notice of meeting or brought before the meeting by or at the direction of our board of directors, or by a stockholder of record on the record date for the meeting, who is entitled to vote at the meeting and who has delivered timely written notice in proper form to our secretary of the stockholder’s intention to bring such business before the meeting. These provisions could have the effect of delaying stockholder actions until the next stockholder meeting that are favored by the holders of a majority of our outstanding voting securities.

Elimination of Stockholder Action by Written Consent. Pursuant to Section 228 of the Delaware General Corporation Law, any action required to be taken at any annual or special meeting of the stockholders may be taken without a meeting, unless the our amended and restated certificate of incorporation provides otherwise. Our amended and restated certificate of incorporation and amended and restated by-laws to be in effect upon completion of this offering eliminate the right of stockholders to act by written consent without a meeting and provide that all stockholder action must be effected at a duly called meeting of stockholders. This provision will make it more difficult for stockholders to take action opposed by the board of directors.

Undesignated Preferred Stock. The authorization of undesignated preferred stock makes it possible for the board of directors, without stockholder approval, to issue preferred stock with voting or other rights or preferences that could impede the success of any attempt to obtain control of us. These and other provisions may have the effect of deferring hostile takeovers or delaying changes in control or management of KAYAK.

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Section 203 of the Delaware General Corporation Law

We are subject to Section 203 of the Delaware General Corporation Law, which prohibits a Delaware corporation from engaging in any business combination with any interested stockholder for a period of three years after the date such stockholder became an interested stockholder, with the following exceptions:

• before such date, our board of directors approved either the business combination or the transaction that resulted in the stockholder becoming an interested holder;

• upon completion of the transaction that resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction began, excluding for purposes of determining the voting stock outstanding (but not the outstanding voting stock owned by the interested stockholder) those shares owned (i) by persons who are directors and also officers and (ii) employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

• on or after such date, the business combination is approved by our board of directors and authorized at an annual or special meeting of the stockholders, and not by written consent, by the affirmative vote of at least 66 2/3% of the outstanding voting stock that is not owned by the interested stockholder.

In general, Section 203 defines business combination to include the following:

• any merger or consolidation involving the corporation and the interested stockholder;

• any sale, transfer, pledge or other disposition of 10% or more of the assets of the corporation involving the interested stockholder;

• subject to certain exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder;

• any transaction involving the corporation that has the effect of increasing the proportionate share of the stock or any class or series of the corporation beneficially owned by the interested stockholder; or

• the receipt by the interested stockholder of the benefit of any loss, advances, guarantees, pledges or other financial benefits by or through the corporation.

Section 203 defines an “interested stockholder” as an entity or person who, together with the person’s affiliates and associates, beneficially owns, or within three years prior to the time of determination of interested stockholder status did own, 15% or more of the outstanding voting stock of the corporation.

Limitations of Liability and Indemnification Matters

Delaware law authorizes corporations to limit or eliminate the personal liability of directors to corporations and their stockholders for monetary damages for breaches of directors’ fiduciary duties as directors. Our amended and restated certificate of incorporation includes a provision that eliminates the personal liability of directors for monetary damages for actions taken as a director, except for liability:

• for breach of duty of loyalty;

• for acts or omissions not in good faith or involving intentional misconduct or knowing violation of law;

• under Section 174 of the Delaware General Corporation Law (unlawful dividends or stock repurchases); or

• for transactions from which the director derived improper personal benefit.

Our amended and restated by-laws provide that we must indemnify and advance expenses to our directors and officers to the fullest extent authorized by Delaware law. We are also expressly authorized to, and do, carry

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directors’ and officers’ insurance for our directors, officers and certain employees for some liabilities. We believe that these indemnification provisions and insurance are useful to attract and retain qualified directors and executive officers. If Delaware law is amended to authorize corporate action further eliminating or limiting the personal liability of a director, then the liability of our directors will be eliminated or limited to the fullest extent permitted by Delaware law, as so amended.

The limitation of liability and indemnification provisions in our amended and restated certificate of incorporation and amended and restated by-laws may discourage stockholders from bringing a lawsuit against directors for breach of their fiduciary duty. These provisions may also have the effect of reducing the likelihood of derivative litigation against directors and officers, even though such an action, if successful, might otherwise benefit us and our stockholders. In addition, your investment may be adversely affected to the extent that, in a class action or direct suit, we pay the costs of settlement and damage awards against directors and officers pursuant to these indemnification provisions. There is currently no pending material litigation or proceeding involving any of our directors, officers or employees for which indemnification is sought.

In addition to the indemnification required in our amended and restated certificate of incorporation and amended and restated by-laws, we also expect our directors and executive officers to execute a new form of indemnification agreement prior to completion of this offering, the form of which we will file as an exhibit to our registration statement of which this prospectus is a part. These agreements provide for the indemnification of our directors and officers for all reasonable expenses and liabilities incurred in connection with any action or proceeding brought against them by reason of the fact that they are or were our agents. We believe that these bylaw provisions and indemnification agreements, as well as our maintaining directors’ and officers’ liability insurance, help to attract and retain qualified persons as directors and officers.

A stockholder’s investment may be harmed to the extent we pay the costs of settlement and damage awards against directors and officers pursuant to these indemnification provisions. Insofar as indemnification for liabilities arising under the Securities Act may be permitted to our directors, officers and controlling persons pursuant to the foregoing provisions, or otherwise, we have been advised that, in the opinion of the SEC, such indemnification is against public policy as expressed in the Securities Act, and is, therefore, unenforceable.

Transfer Agent and Registrar

The transfer agent and registrar for our Class A common stock will be             .

Listing

We applied to list our Class A common stock on The NASDAQ Stock Market under the trading symbol “KYAK.”

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MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS TO NON-U.S. HOLDERS

The following is a summary of material U.S. federal income tax consequences of the purchase, ownership and disposition of our common stock to a non-U.S. holder that purchases shares of our common stock for cash in this offering. For purposes of this summary, a “non-U.S. holder” means a beneficial owner of our common stock that is, for U.S. federal income tax purposes:

• a nonresident alien individual;

• a foreign corporation (or an entity treated as a foreign corporation for U.S. federal income tax purposes); or

• a foreign estate or foreign trust.

In the case of a holder that is classified as a partnership for U.S. federal income tax purposes, the tax treatment of a partner in that partnership generally will depend upon the status of the partner and the activities of the partner and the partnership. If you are a partner in a partnership holding our common stock, then you should consult your own tax advisor.

This summary is based upon the provisions of the U.S. Internal Revenue Code of 1986, as amended, or the Code, the Treasury regulations promulgated thereunder and judicial and published administrative interpretations thereof, all as of the date hereof. Those authorities may be changed, perhaps retroactively, so as to result in U.S. federal income tax consequences different from those summarized below. We cannot assure you that a change in law, possibly with retroactive application, will not alter significantly the tax considerations that we describe in this summary. We have not sought, and do not plan to seek, any ruling from the U.S. Internal Revenue Service, or the IRS, with respect to statements made and the conclusions reached in the following summary, and there can be no assurance that the IRS or a court will agree with our statements and conclusions.

This summary does not address all aspects of U.S. federal income taxes that may be relevant to non-U.S. holders in light of their personal circumstances, and does not deal with federal taxes other than the U.S. federal income tax or with non-U.S., state or local tax considerations. Special rules, not discussed here, may apply to certain non-U.S. holders, including:

• U.S. expatriates and former long-term residents of the U.S.;

• foreign governments or entities that they control;

• controlled foreign corporations (and their stockholders);

• passive foreign investment companies (and their stockholders); and

• investors in pass-through entities that are subject to special treatment under the Code.

Such non-U.S. holders should consult their own tax advisors to determine the U.S. federal, state, local and non-U.S. tax consequences that may be relevant to them.

This summary applies only to a non-U.S. holder that holds our common stock as a capital asset (within the meaning of Section 1221 of the Code). Non-U.S. holders that hold our stock other than as capital assets should consult their own tax advisors to determine the U.S. federal, state, local and non-U.S. tax consequences that may be relevant to them.

If you are considering the purchase of our common stock, you should consult your own tax advisor concerning the particular U.S. federal income tax consequences to you of the purchase, ownership and disposition of our common stock, as well as the consequences to you arising under U.S. tax laws other than the federal income tax law or under the laws of any other taxing jurisdiction.

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Dividends

If we make a distribution of cash or property (other than certain stock distributions) with respect to our common stock, or effect one of certain redemptions that are treated as distributions with respect to our common stock, any such distributions or redemptions will be treated as a dividend for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits (as determined under U.S. federal income tax principles). Dividends paid to you generally will be subject to withholding of U.S. federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty. However, dividends that are effectively connected with the conduct of a trade or business by you within the U.S. and, where a tax treaty applies, that are generally attributable to a permanent establishment or fixed base in the U.S., as defined under the applicable treaty, are not subject to the withholding tax, but instead are subject to U.S. federal income tax on a net income basis at the graduated individual or corporate U.S. federal income tax rates generally applicable to U.S. persons. Certain certification and disclosure requirements, including delivery of a properly executed IRS Form W-8ECI, must be satisfied for that effectively connected income to be exempt from withholding. Any such effectively connected dividends received by a foreign corporation may be subject to an additional “branch profits tax” at a 30% rate or such lower rate as may be specified by an applicable income tax treaty.

If the amount of a distribution paid on our common stock exceeds our current and accumulated earnings and profits, such excess will be allocated ratably among the shares of common stock with respect to which the distribution is paid and treated first as a tax-free return of capital to the extent of your adjusted tax basis in each such share, and thereafter as capital gain from a sale or other disposition of such share that is taxed to you as described below under the heading “—Gain on Disposition of Common Stock.” Your adjusted tax basis in a share is generally the purchase price of the share, reduced by the amount of any such tax-free return of capital with respect to that share.

If you wish to claim the benefit of an applicable income tax treaty to avoid or reduce withholding of U.S. federal income tax on dividends, then you must (a) provide the withholding agent with a properly completed IRS Form W-8BEN (or other applicable form) and certify under penalties of perjury that you are not a U.S. person and are eligible for treaty benefits, or (b) if our common stock is held through one of certain foreign intermediaries, satisfy the relevant certification requirements of applicable U.S. Treasury regulations. Form W-8BEN must be provided to us or our paying agent prior to the payment of dividends and may be required to be updated periodically. Special certification and other requirements apply to certain non-U.S. holders that act as intermediaries (including partnerships).

If you are eligible for a reduced rate of U.S. federal income tax pursuant to an income tax treaty, then you may obtain a refund or credit of any excess amounts withheld by timely filing an appropriate claim with the IRS.

Gain on Disposition of Common Stock

You generally will not be subject to U.S. federal income tax with respect to gain realized on the sale, exchange or other taxable disposition of our common stock, unless:

• the gain is effectively connected with a trade or business you conduct in the U.S., and, where a tax treaty applies, is attributable to a permanent establishment or fixed base in the U.S. as defined under the applicable treaty;

• if you are an individual, you are present in the U.S. for 183 days or more in the taxable year of the sale, exchange or other taxable disposition, and certain other conditions are met; or

• we are or have been during a specified testing period a “United States real property holding corporation” for U.S. federal income tax purposes, and, in the case where shares of our common stock are regularly traded on an established securities market, you have owned, directly or indirectly, more than 5% of our common stock at any time within the shorter of the five-year period preceding the disposition or your holding period for your shares of our common stock. There can be no assurance that our common stock will be treated as regularly traded on an established securities market for this purpose.

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If your gain is described in the first or third bullet point above, you will be subject to tax on the net gain derived from the sale at the graduated individual or corporate U.S. federal income tax rates generally applicable to U.S. persons or at such lower rate as may be specified by an applicable income tax treaty. If you are a foreign corporation and your gain is described in the first bullet point above, you may also be subject to a branch profits tax at a rate of 30% or at such lower rate as may be specified by an applicable income tax treaty. If you are an individual described in the second bullet point above, you will be subject to a flat 30% tax on the gain derived from the sale, which may be offset by U.S.-source capital losses. The gross proceeds from transactions that generate gains described in the third bullet point above will generally be subject to a 10% withholding tax, which you may claim as a credit against your federal income tax liability.

We believe that we have not been and are not, and we do not anticipate becoming, a “United States real property holding corporation” for U.S. federal income tax purposes. Generally, we will be a “United States real property holding corporation” if the fair market value of our U.S. real property interests equals or exceeds 50% of the sum of the fair market values of our worldwide real property interests and other assets used or held for use in a trade or business, all as determined for U.S. federal income tax purposes.

Information Reporting and Backup Withholding

We must report annually to the IRS and to you the amount of dividends and other distributions paid to you and the amount of tax, if any, withheld with respect to those distributions. The IRS may make this information available to the tax authorities in the country in which you are resident.

In addition, you may be subject to information reporting requirements and backup withholding with respect to dividends paid on, and the proceeds of disposition of, shares of our common stock, unless, generally, you certify under penalties of perjury (usually on IRS Form W-8BEN) that you are not a U.S. person or you otherwise establish an exemption. The backup withholding rate is 28% and is scheduled to increase to 31% in 2013. Additional rules relating to information reporting requirements and backup withholding with respect to payments of the proceeds from the disposition of shares of our common stock are as follows:

• If the proceeds are paid to or through the U.S. office of a broker, the proceeds generally will be subject to backup withholding and information reporting, unless you certify under penalties of perjury (usually on IRS Form W-8BEN) that you are not a U.S. person or you otherwise establish an exemption.

• If the proceeds are paid to or through a non-U.S. office of a broker that is not a U.S. person and is not a foreign person with certain specified U.S. connections, which we refer to below as a “U.S.-related person,” information reporting and backup withholding generally will not apply.

• If the proceeds are paid to or through a non-U.S. office of a broker that is a U.S. person or a U.S.-related person, the proceeds generally will be subject to information reporting (but not to backup withholding), unless you certify under penalties of perjury (usually on IRS Form W-8BEN) that you are not a U.S. person.

Backup withholding is not a tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against your U.S. federal income tax liability, provided the required information is timely furnished by you to the IRS.

Foreign Accounts

Legislation enacted in 2010 will impose withholding taxes on certain types of payments made to “foreign financial institutions” and other non-U.S. entities after December 31, 2013 unless those institutions and entities meet additional certification, information reporting and other requirements. The legislation will generally impose a 30% withholding tax on dividends on, or gross proceeds from the sale or other disposition of, our common stock paid to a foreign financial institution unless the foreign financial institution enters into an agreement with

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the U.S. Treasury to, among other things, (i) undertake to identify accounts held by certain U.S. persons (including certain equity and debt holders of such institution) or by U.S.-owned foreign entities, (ii) annually report certain information about such accounts, and (iii) withhold 30% on payments to account holders whose actions prevent it from complying with these reporting and other requirements. In addition, subject to certain exceptions, the legislation will impose a 30% withholding tax on the same types of payments to an entity that is not a foreign financial institution unless the entity certifies that it does not have any substantial U.S. owners (which generally include any U.S. persons who directly or indirectly own more than 10% of the entity) or furnishes identifying information regarding each such substantial U.S. owner. These withholding taxes would be imposed on dividends paid on our common stock after December 31, 2013, and on gross proceeds from sales or other dispositions of our common stock after December 31, 2014. We will not pay any additional amounts to non-U.S. holders in respect of any amounts withheld. Prospective investors should consult their tax advisors regarding this legislation.

The summary of material U.S. federal income tax consequences above is included for general information purposes only. Potential purchasers of our common stock are urged to consult their own tax advisors to determine the U.S. federal, state, local and non-U.S. tax considerations of purchasing, owning and disposing of our common stock.

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SHARES ELIGIBLE FOR FUTURE SALE

Before this offering, there has not been a public market for our common stock. As described below, only a limited number of shares currently outstanding will be available for sale immediately after this offering due to contractual and legal restrictions on resale. Nevertheless, future sales of substantial amounts of our Class A common stock, including shares issued upon conversion of outstanding Class B common stock or upon exercise of outstanding options, in the public market after the restrictions lapse, or the possibility of such sales, could cause the prevailing market price of our Class A common stock to fall or impair our ability to raise equity capital in the future.

Based on the number of shares of common stock outstanding as of             , upon completion of this offering,              shares of common stock will be outstanding (assuming no options or warrants are exercised, including the underwriters’ over-allotment option). All of the shares of Class A common stock sold in this offering will be freely tradable unless purchased by our affiliates. The remaining              shares of common stock outstanding after this offering will be restricted as a result of securities laws or lock-up agreements as described below. Following the expiration of the lock-up period, all shares will be eligible for resale in compliance with Rule 144 or Rule 701. “Restricted securities” as defined under Rule 144 were issued and sold by us in reliance on exemptions from the registration requirements of the Securities Act. These shares may be sold in the public market only if registered or pursuant to an exemption from registration, such as Rule 144 or Rule 701 under the Securities Act.

Rule 144

In general, pursuant to Rule 144 under the Securities Act, as in effect on the date of this prospectus, a person who is one of our affiliates and has beneficially owned shares of our common stock for at least six months would be entitled to sell within any three-month period a number of shares that does not exceed the greater of:

• one percent of the number of shares of common stock then outstanding, which will equal approximately             shares immediately after the completion of this offering; and

• the average weekly trading volume of such Class A common stock on The NASDAQ Stock Market during the four calendar weeks preceding the filing of a notice on Form 144 with respect to the sale.

Sales under Rule 144 are also subject to manner of sale provisions and notice requirements and to the availability of current public information about us. For a person who has not been deemed to have been one of our affiliates at any time during the 90 days preceding a sale, sales of our securities held longer than six months, but less than one year, will be subject only to the current public information requirement.

A person who is not deemed to have been one of our affiliates at any time during the 90 days preceding a sale, and who has beneficially owned the shares proposed to be sold for at least one year, including the holding period of any prior owner other than an affiliate, is entitled to sell the shares without complying with the manner of sale, public information, volume limitation or notice provisions of Rule 144. All shares of our common stock will qualify for resale under Rule 144 within a minimum of 180 days of the date of this prospectus, subject to the lock-up agreements.

Rule 701

Any of our employees, officers or directors who purchased shares under a written compensatory plan or contract may be entitled to sell them in reliance on Rule 701. Rule 701 permits affiliates to sell their Rule 701 shares under Rule 144 without complying with the holding period requirements of Rule 144. Rule 701 further provides that nonaffiliates may sell these shares in reliance on Rule 144 without complying with the holding period, public information, volume limitation or notice provisions of Rule 144. All holders of Rule 701 shares are required to wait until 90 days after the date of this prospectus before selling those shares. However, all shares issued under Rule 701 are subject to lock-up agreements and will only become eligible for sale when the 180-day lock-up agreements expire or such shares are earlier released.

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Lock-Up Agreements

In connection with this offering, we, all directors and officers and certain holders of our outstanding stock, stock options and other equity awards that hold             % of the outstanding shares of our common stock (including the shares issuable pursuant to the automatic adjustment based on an assumed initial public offering price of $             per share) have agreed that, without the prior written consent of Morgan Stanley, on behalf of the underwriters, we and they will not, during the period ending 180 days after the date of this prospectus:

• offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend or otherwise transfer or dispose of, directly or indirectly, any shares of our common stock or any securities convertible into or exercisable or exchangeable for shares of common stock;

• enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of our common stock; or

• file any registration statement with the SEC relating to the offering of any shares of our common stock or any securities convertible into or exercisable or exchangeable for our common stock, except for the filing of a registration statement on Form S-8 relating to the offering of securities in accordance with the terms of a plan in effect on the date hereof and as described herein,

whether any such termination described above is to be settled by delivery of our common stock or such other securities, in cash or otherwise. In addition, if any shares are issued pursuant to the private placement purchase rights, such shares shall also be subject to the lock-up agreement described above.

The restrictions in the immediately preceding paragraph do not apply in certain circumstances as described in the section entitled “Underwriters.”

The 180-day restricted period described herein will be extended if:

• during the last 17 days of the restricted period, we issue an earnings release or material news or a material event relating to us occurs; or

• prior to the expiration of the restricted period, we announce that we will release earnings results during the 16-day period beginning on the last day of the restricted period,

in which case the restrictions described above shall continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event unless Morgan Stanley waives such extension.

For additional information, see “Underwriters.”

Registration Rights

We are party to an Investor Rights Agreement, which provides that holders of our common stock issuable or issued upon conversion of our convertible preferred stock have the right to require us to register any or all of their shares under the Securities Act at our expense, subject to certain limitations. Registration of shares held by these stockholders under the Securities Act would result in these shares becoming freely tradable without restriction under the Securities Act immediately upon effectiveness of the registration, subject to the expiration of, or release from, the lock-up period. See “Certain Relationships and Related Party Transactions—Related Party Transactions—Investor Rights Agreement” for more information.

Equity Plans

As soon as practicable after the completion of this offering, we intend to file a registration statement on Form S-8 under the Securities Act covering the shares of our common stock issuable upon exercise of outstanding options under our 2004 Stock Incentive Plan, Third Amended and Restated 2005 Equity Incentive Plan and 2012 Equity Incentive Plan. Such registration statement will become effective immediately upon filing, and shares covered by this registration statement will thereupon be eligible for sale in the public markets, subject to Rule 144 limitations applicable to affiliates and any lock-up agreements. For a more complete discussion of our stock plans, see “Executive Compensation—Compensation Discussion and Analysis—Equity-Based Compensation.”

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UNDERWRITERS

Under the terms and subject to the conditions contained in an underwriting agreement dated the date of this prospectus, the underwriters named below, for whom Morgan Stanley & Co. LLC and Deutsche Bank Securities Inc., are acting as representatives, have severally agreed to purchase, and we have agreed to sell to them, severally, the number of shares indicated below:

Name	Number of Shares
Morgan Stanley & Co. LLC
Deutsche Bank Securities Inc.
Piper Jaffray & Co.
Stifel, Nicolaus & Company, Incorporated
Pacific Crest Securities LLC
Total

The underwriters and the representatives are collectively referred to as the “underwriters” and the “representatives,” respectively. The underwriters are offering the shares of Class A common stock subject to their acceptance of the shares from us and subject to prior sale. The underwriting agreement provides that the obligations of the several underwriters to pay for and accept delivery of the shares of Class A common stock offered by this prospectus are subject to the approval of certain legal matters by their counsel and to certain other conditions. The underwriters are obligated to take and pay for all of the shares of Class A common stock offered by this prospectus if any such shares are taken. However, the underwriters are not required to take or pay for the shares covered by the underwriters’ over-allotment option described below.

The underwriters initially propose to offer part of the shares of Class A common stock directly to the public at the offering price listed on the cover page of this prospectus and part to certain dealers. After the initial offering of the shares of Class A common stock, the offering price and other selling terms may from time to time be varied by the representatives.

We granted to the underwriters an option, exercisable for 30 days from the date of this prospectus, to purchase up to an aggregate of             additional shares of Class A common stock at the public offering price listed on the cover page of this prospectus, less underwriting discounts and commissions. The underwriters may exercise this option solely for the purpose of covering over-allotments, if any, made in connection with the offering of the shares of Class A common stock offered by this prospectus. To the extent the option is exercised, each underwriter will become obligated, subject to certain conditions, to purchase about the same percentage of the additional shares of Class A common stock as the number listed next to the underwriter’s name in the preceding table bears to the total number of shares of Class A common stock listed next to the names of all underwriters in the preceding table.

The following table shows the per share and total public offering price, underwriting discounts and commissions and proceeds before expenses to us. These amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase up to an additional             shares of Class A common stock from us.

	Per Share		Total
	Without Over-allotment	With Over-allotment	Without Over-allotment	With Over-allotment
Public offering price
Underwriting discounts and commissions to be paid by us
Proceeds, before expenses, to us

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The estimated offering expenses payable by us, exclusive of the underwriting discounts and commissions, are approximately $            . The underwriters have agreed to reimburse us for certain of our offering expenses.

The underwriters have informed us that they do not intend sales to discretionary accounts to exceed 5% of the total number of shares of Class A common stock offered by them.

We applied to list our Class A common stock on The NASDAQ Stock Market under the trading symbol “KYAK.”

We, all directors and officers and certain holders of our outstanding stock, stock options and other equity awards that hold         % of the outstanding shares of our common stock (including the shares issuable pursuant to the automatic adjustment based on an assumed initial public offering price of $             per share) have agreed that, without the prior written consent of Morgan Stanley, on behalf of the underwriters, we and they will not, during the period ending 180 days after the date of this prospectus:

• offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend or otherwise transfer or dispose of, directly or indirectly, any shares of common stock or any securities convertible into or exercisable or exchangeable for shares of our common stock;

• enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of our common stock; or

• file any registration statement with the SEC relating to the offering of any shares of our common stock or any securities convertible into or exercisable or exchangeable for our common stock, except for the filing of a registration statement on Form S-8 relating to the offering of securities in accordance with the terms of a plan in effect on the date hereof and as described herein,

whether any such transaction described above is to be settled by delivery of our common stock or such other securities, in cash or otherwise. In addition, if any shares are issued pursuant to the private placement purchase rights, such shares shall also be subject to the lock-up agreement described above. Also, each such person agrees that, without the prior written consent of Morgan Stanley, on behalf of the underwriters, it will not, during the restricted period, make any demand for, or exercise any right with respect to, the registration of any shares of our common stock or any security convertible into or exercisable or exchangeable for our common stock.

The restrictions described in the immediately preceding paragraph do not apply to:

• the sale of shares to the underwriters;

• the sale or transfer to us of any shares of our common stock or any security convertible into our common stock by certain of our employees pursuant to the terms of (i) any restricted stock award upon the termination of such employee’s employment with us or (ii) any contractual obligation of us to repurchase such shares arising from our acquisition of swoodoo, which obligation exists on the date of such agreement and is described herein;

• the issuance of shares of our common stock upon the exercise of an option or warrant or the conversion of a security outstanding on the date hereof which the underwriters have been advised in writing (including any description thereof in the registration statement of which this prospectus is a part) or grants of stock options or restricted stock in accordance with the terms of a plan in effect upon completion of this offering and described herein or the issuance by us of shares of our common stock upon the exercise thereof; provided, that any recipient agrees to the restrictions set forth herein;

• the sale or issuance of or entry into an agreement to sell or issue shares of our common stock (or options, warrants or convertible securities relating to shares of our common stock) in connection with bona fide mergers or acquisitions, joint ventures, commercial relationships or other strategic transactions; provided, that the aggregate number of shares of such common stock, options, warrants or

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convertible securities shall not exceed 10% of the total number of shares of our common stock (or options or warrants relating to shares of our common stock) issued and outstanding immediately following the completion of this offering and the recipients of such shares or other securities agree to the restrictions set forth herein;

• transactions by persons other than us relating to shares of our common stock or other securities acquired in open market transactions after the completion of the offering of the shares, provided that no filing under Section 16(a) of the Exchange Act shall be required or shall be voluntarily made in connection with subsequent sales of our common stock or other securities acquired in such open market transactions;

• transfers by any person other than us of shares of our common stock or any security convertible into our common stock as a bona fide gift, provided that each donee shall enter into a written agreement accepting the restrictions set forth herein and no filing under Section 16(a) of the Exchange Act, reporting a reduction in beneficial ownership of shares of our common stock, shall be required or shall be voluntarily made during the restricted period;

• distributions by any persons other than us of shares of common stock or any security convertible into our common stock to partners, members, stockholders, affiliates or any entity which is directly or indirectly controlled by, or is under common control with, such person, provided that each distributee shall enter into a written agreement accepting the restrictions set forth herein and no filing under Section 16(a) of the Exchange Act, reporting a reduction in beneficial ownership of shares of our common stock, shall be required or shall be voluntarily made during the restricted period;

• the establishment of a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer of shares of our common stock, provided that such plan does not provide for the transfer of our common stock during the restricted period and no public announcement or filing under the Exchange Act regarding the establishment of such plan shall be required of or voluntarily made by or on behalf of such person or us; or

• transfers by certain officers and directors of shares of our common stock or any security convertible into common stock to any immediate family member (including any former spouse) and certain subsequent transfers by such family member or to a trust or other entity for the benefit of such family member to comply with the provisions of (i) any order or settlement resulting from any legal proceedings or (ii) any irrevocable trust, provided that each transferee shall enter into a written agreement accepting the restrictions set forth herein.

The 180-day restricted period described above will be extended if:

• during the last 17 days of the restricted period, we issue an earnings release or material news or a material event relating to us occurs; or

• prior to the expiration of the restricted period, we announce that we will release earnings results during the 16-day period beginning on the last day of the restricted period,

in which case the restrictions described above shall continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event unless Morgan Stanley waives such extension.

In addition, each such person has agreed that it will not engage in any transaction that may be restricted during the 34-day period beginning on the last day of the 180-day restricted period unless it requests and receives prior written confirmation from us or Morgan Stanley that the restrictions described above have expired.

To facilitate the offering of the Class A common stock, the underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the Class A common stock. Specifically, the underwriters may

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sell more shares than they are obligated to purchase under the underwriting agreement, creating a short position. A short sale is covered if the short position is no greater than the number of shares available for purchase by the underwriters under the over- allotment option. The underwriters can close out a covered short sale by exercising the over-allotment option or purchasing shares in the open market. In determining the source of shares to close out a covered short sale, the underwriters will consider, among other things, the open market price of shares compared to the price available under the over-allotment option. The underwriters may also sell shares in excess of the over-allotment option, creating a naked short position. The underwriters must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the Class A common stock in the open market after pricing that could adversely affect investors who purchase in this offering. As an additional means of facilitating this offering, the underwriters may bid for, and purchase, shares of Class A common stock in the open market to stabilize the price of the Class A common stock. The underwriters also may impose a penalty bid. Penalty bids permit the underwriters to reclaim a selling concession from a syndicate member when the underwriters repurchase shares originally sold by that syndicate member in order to cover syndicate short positions or make stabilizing purchases. These activities may raise or maintain the market price of the Class A common stock above independent market levels or prevent or retard a decline in the market price of the Class A common stock. The underwriters are not required to engage in these activities and may end any of these activities at any time.

We and the underwriters have agreed to indemnify each other against certain liabilities, including liabilities under the Securities Act.

A prospectus in electronic format may be made available on websites maintained by one or more underwriters or selling group members, if any, participating in this offering. The representatives may agree to allocate a number of shares of Class A common stock to underwriters for sale to their online brokerage account holders. Internet distributions will be allocated by the representatives to underwriters that may make Internet distributions on the same basis as other allocations.

From time to time, certain of the underwriters or their respective affiliates may engage in transactions with us and have performed and may perform investment banking and advisory services for us in the ordinary course of their business for which they have received or would receive customary fees and expenses.

Pricing of the Offering

Prior to this offering, there has been no public market for our common stock. The initial public offering price was determined by negotiations between us and the representatives. Among the factors considered in determining the initial public offering price were our future prospects and those of our industry in general, our sales, earnings and certain other financial and operating information in recent periods, and the price-earnings ratios, price-sales ratios, market prices of securities and certain financial and operating information of companies engaged in activities similar to ours. The estimated initial public offering price range set forth on the cover page of this prospectus is subject to change as a result of market conditions and other factors. We cannot assure you that the prices at which the shares will sell in the public market after this offering will not be lower than the initial public offering price or that an active trading market in our Class A common stock will develop and continue after this offering.

European Economic Area

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a “Relevant Member State”) an offer to the public of any shares of our Class A common stock may not be made in that Relevant Member State, except that an offer to the public in that Relevant Member State of any shares of our Class A common stock may be made at any time under the following exemptions under the Prospectus Directive, if they have been implemented in that Relevant Member State:

(a) to any legal entity which is a qualified investor as defined in the Prospectus Directive;

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(b) to fewer than 100 or, if the Relevant Member State has implemented the relevant provision of the 2010 PD Amending Directive, 150, natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the representatives for any such offer; or

(c) in any other circumstances falling within Article 3(2) of the Prospectus Directive, provided that no such offer of shares of our common stock shall result in a requirement for the publication by us or any underwriter of a prospectus pursuant to Article 3 of the Prospectus Directive.

For the purposes of this provision, the expression an “offer to the public” in relation to any shares of our Class A common stock in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and any shares of our Class A common stock to be offered so as to enable an investor to decide to purchase any shares of our Class A common stock, as the same may be varied in that Member State by any measure implementing the Prospectus Directive in that Member State, the expression “Prospectus Directive” means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the Relevant Member State), and includes any relevant implementing measure in the Relevant Member State, and the expression “2010 PD Amending Directive” means Directive 2010/73/EU.

United Kingdom

Each underwriter has represented and agreed that:

(a) it has only communicated or caused to be communicated and will only communicate or cause to be communicated an invitation or inducement to engage in investment activity (within the meaning of Section 21 of the FSMA) received by it in connection with the issue or sale of the shares of our Class A common stock in circumstances in which Section 21(1) of the FSMA does not apply to us; and

(b) it has complied and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the shares of our Class A common stock in, from or otherwise involving the United Kingdom.

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CONCURRENT PRIVATE PLACEMENTS

In consideration for the receipt of certain elections, waivers, consents and amendments agreed to by our existing stockholders, as further described in the section titled “Certain Relationships and Related Party Transactions—Related Party Transactions—Election and Amendment Agreement,” on April 19, 2012, we entered into an Election and Amendment Agreement with certain existing stockholders, or the eligible holders, pursuant to which we granted certain of the eligible holders the right to purchase from us up to an aggregate of $9.2 million of Class A common stock at the initial public offering price. We refer to these as the private placement purchase rights. The private placement purchase rights must be exercised, if at all, within five business days after the closing of this initial public offering; furthermore, the private placement purchase rights will not apply if our initial public offering price equals or exceeds $31.09 per share.

Based on an assumed initial public offering price of $             per share, which is the midpoint of the initial public offering price range set forth on the cover of the prospectus, we would issue an aggregate of              additional Class A common shares and receive $9.2 million in gross proceeds, if each eligible holder with private placement purchase rights exercised them in full.

Pursuant to the Election and Amendment Agreement, we have also agreed that we will issue to the eligible holders additional shares of Class A common stock if our initial public offering price is less than $27.00 per share. In such event, the total number of additional shares will be calculated by taking the amount by which $27.00 exceeds the initial public offering price per share, dividing that excess amount by the initial public offering price per share and, finally, multiplying the result by             , which is the number of shares of Series D preferred stock held by the eligible holders. We refer to this as the automatic adjustment. Any additional shares of Class A common stock issued pursuant to the automatic adjustment will be issued in consideration for the receipt of certain elections, waivers, consents and amendments agreed to by the eligible holders, but for no additional cash consideration.

Based on an assumed initial public offering price of $             per share, which is the midpoint of the range set forth on the cover of the prospectus, we would issue an aggregate of              additional shares of Class A common stock pursuant to the automatic adjustment.

We will not pay any underwriting discounts or commissions on the shares issued in these concurrent private placements.

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Throughout this prospectus we provide information assuming that the initial public offering price per share of Class A common stock in this offering is $             , which is the midpoint of the price range set forth on the cover page of this prospectus. However, as described above, the number of shares issuable pursuant to the concurrent private placements will change if the initial public offering price per share in this offering differs from the midpoint of the estimated price range. The following table sets forth various prices per share below, within and above the price range set forth on the cover page of this prospectus, and illustrates the impact of such deviations on the number of shares which are issuable pursuant to the concurrent private placements. This table is for illustrative purposes only, and the actual initial offering price per share in this offering might not match any of the example prices per share set forth below and may be more or less than any of the prices per share set forth below. The information in the table assumes full exercise of the private placement purchase right and no exercise of the underwriters’ over-allotment option.

	Initial Public Offering Price per Share of Class A Common Stock
	$	$	$	$	$
Private placement purchase right shares
Automatic adjustment shares
Total shares subject to the concurrent private placements
Total common stock outstanding after this offering
Concurrent private placement shares as a percentage of total common stock outstanding after this offering

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LEGAL MATTERS

The validity of the shares of our Class A common stock offered in the offering will be passed upon for us by Bingham McCutchen LLP, Boston, Massachusetts. Davis Polk & Wardwell LLP, New York, New York is representing the underwriters in this offering.

EXPERTS

The consolidated financial statements of KAYAK Software Corporation and subsidiaries as of December 31, 2010, and December 31, 2011, and for each of the three years in the period ended December 31, 2011, appearing in this prospectus have been so included in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in accounting and auditing.

This prospectus includes reference to a June 2011 market research study conducted by TNS Custom Research, Inc. TNS Custom Research, Inc. received a flat rate fee from us for completion of this study. TNS Custom Research, Inc. does not have any interest in the securities of KAYAK.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We have filed with the SEC a registration statement on Form S-1, including exhibits and schedules, under the Securities Act with respect to the Class A common stock to be sold in this offering. This prospectus, which constitutes a part of the registration statement, does not contain all of the information set forth in the registration statement or the exhibits and schedules that are part of the registration statement. Any statements made in this prospectus as to the contents of any contract, agreement or other document are not necessarily complete. You should refer to the registration statement and its exhibits for additional information. With respect to each such contract, agreement or other document filed as an exhibit to the registration statement, we refer you to the exhibit for a more complete description of the matter involved, and each statement in this prospectus shall be deemed qualified by this reference. You may read and copy all or any portion of the registration statement or any reports, statements or other information in the files at the following public reference facilities of the SEC:

Public Reference Room

100 F Street, NE

Washington, DC 20549

You can request copies of these documents upon payment of a duplicating fee by writing to the SEC. Please call the SEC at 1-800-SEC-0330 for further information on the operation of the public reference facilities. When we complete this offering, we will also be required to file annual, quarterly and special reports, proxy statements and other information with the SEC. Our filings, including the registration statement, will also be available to you on the Internet website maintained by the SEC at www.sec.gov.

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KAYAK SOFTWARE CORPORATION

INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

	Page
Report of Independent Registered Public Accounting Firm		F-2
Consolidated Balance Sheets as of December 31, 2010 and 2011		F-3
Consolidated Statements of Operations for the Years Ended December 31, 2009, 2010 and 2011		F-4
Consolidated Statements of Changes in Stockholders’ Equity (Deficit) for the Years Ended December 31, 2009, 2010 and 2011		F-5
Consolidated Statements of Cash Flows for the Years Ended December 31, 2009, 2010 and 2011		F-6
Notes to Consolidated Financial Statements		F-7
Financial Statement Schedule:
Schedule II - Consolidated Valuation and Qualifying Accounts		F-30

F-1

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Stockholders of

KAYAK Software Corporation:

In our opinion, the accompanying consolidated balance sheets and the related consolidated statements of operations, of changes in stockholders deficit, and of cash flows present fairly, in all material respects, the financial position of KAYAK Software Corporation and its subsidiaries at December 31, 2011 and 2010, and the results of their operations and their cash flows for each of the three years in the period ended December 31, 2011 in conformity with accounting principles generally accepted in the United States of America. In addition, in our opinion the financial statement schedule listed in the accompanying index presents fairly, in all material respects, the information set forth therein when read in conjunction with the related consolidated financial statements. These financial statements and financial statement schedule are the responsibility of the Company’s management. Our responsibility is to express an opinion on these financial statements and financial statement schedule based on our audits. We conducted our audits of these statements in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

/s/ PricewaterhouseCooper LLP

Stamford, CT

March 9, 2012

F-2

KAYAK Software Corporation and Subsidiaries

Consolidated Balance Sheets

(In thousands, except share and per share amounts)

	December 31,						Pro forma at December 31,
	2010			2011			2011(1)
							(unaudited)
Assets
Current assets
Cash and cash equivalents	$	34,966		$	35,127		$	35,127
Marketable securities		4,362			11,198			11,198
Accounts receivable, net of allowance for doubtful accounts of $1,804 and $3,581 at December 31, 2010 and 2011, respectively		30,213			37,332			37,332
Deferred tax asset		3,685			2,212			2,212
Prepaid expenses and other current assets		5,009			5,425			5,425
Total current assets		78,235			91,294			91,294
Property and equipment, net		3,434			5,474			5,474
Intangible assets, net		32,719			17,684			17,684
Goodwill		152,164			155,677			155,677
Deferred tax asset		3,157			7,488			7,488
Other assets		198			331			331
Total assets	$	269,907		$	277,948		$	277,948
Liabilities and stockholders’ (deficit) equity
Current liabilities
Accounts payable	$	4,673		$	9,514		$	9,514
Accrued expenses and other current liabilities		14,933			16,220			16,220
Total current liabilities		19,606			25,734			25,734
Warrant liability		1,235			1,150			1,150
Acquisition-related put liability		1,262			—			—
Deferred tax liability		12,327			4,202			4,202
Other long-term liabilities		178			1,092			1,092
Total liabilities		34,608			32,178			32,178
Redeemable convertible preferred stock
Series A Redeemable Convertible Preferred Stock, $0.001 par value (liquidation preference of $13,002 at December 31, 2011); 6,600,000 shares authorized, issued and outstanding		9,306			9,702			—
Series A-1 Redeemable Convertible Preferred Stock, $0.001 par value; (liquidation preference of $3,180 at December 31, 2011); 1,176,051 shares authorized, issued and outstanding		2,256			2,355			—
Series B Redeemable Convertible Preferred Stock, $0.001 par value; (liquidation preference of $13,388 at December 31, 2011); 4,989,308 shares authorized, issued and outstanding		9,468			9,888			—
Series B-1 Redeemable Convertible Preferred Stock, $0.001 par value (liquidation preference of $5,526 at December 31, 2011); 2,138,275 shares authorized, issued and outstanding		3,846			4,026			—
Series C Redeemable Convertible Preferred Stock, $0.001 par value (liquidation preference of $21,122 at December 31, 2011); 3,897,084 shares authorized and 3,855,180 shares issued and outstanding		14,681			15,372			—
Series D Redeemable Convertible Preferred Stock, $.001 par value (liquidation preference of $289,139 at December 31, 2011); 8,075,666 shares authorized and 8,008,842 shares issued and outstanding		196,192			206,151			—
Total redeemable convertible preferred stock		235,749			247,494			—
Commitments and contingencies (Note 10)
Stockholders’ (deficit) equity
Common stock, $0.001 par value; 45,000,000 shares authorized, 7,380,008 shares issued and outstanding at December 31, 2010; 45,000,000 shares authorized, 7,025,467 shares issued and outstanding at December 31, 2011		7			7			—
Class A common stock, $0.001 par value: no shares authorized, issued and outstanding, on an actual basis(2)		—			—			—
Class B common stock, par value $0.001: no shares authorized, issued and outstanding on an actual basis; 45,000,000 shares authorized, 33,793,123 issued and outstanding, on a pro forma basis		—			—			34
Additional paid-in capital		12,467			3,296			250,763
Cumulative translation adjustment		829			(977	)		(977	)
Accumulated deficit		(13,753	)		(4,050	)		(4,050	)
Total stockholders’ (deficit) equity		(450	)		(1,724	)		245,770
Total liabilities and stockholders’ (deficit) equity	$	269,907		$	277,948		$	277,948

(1) The unaudited pro forma balance sheet gives effect to the conversion of all outstanding shares of our common stock and our redeemable convertible preferred stock into 33,793,123 shares of Class B common stock upon the completion of an initial public offering.

(2) Upon the completion of an initial public offering, we will have two classes of common stock. All existing shares will convert into Class B Common stock and shares sold in the initial public offering will be Class A common stock. The rights of the holders of our common stock are identical except with respect to voting and conversion rights.

See notes to consolidated financial statements

F-3

KAYAK Software Corporation and Subsidiaries

Consolidated Statements of Operations

(In thousands, except share and per share amounts)

	Year Ended December 31,
	2009			2010			2011
Revenues	$	112,698		$	170,698		$	224,534
Cost of revenues (excludes depreciation and amortization)		15,362			15,630			18,598
Selling, general and administrative expenses:
Marketing		57,389			91,721			111,018
Personnel		22,638			29,764			40,785
Other general and administrative expenses		6,568			9,967			16,400
Total selling, general and administrative expenses (excludes depreciation and amortization)		86,595			131,452			168,203
Depreciation and amortization		5,380			6,821			8,486
Impairment of intangible assets		—			—			14,980
Income from operations		5,361			16,795			14,267
Other income (expense)
Interest income		443			107			111
Interest expense		(322	)		—			—
Realized gain on investment		—			459			—
Other income (expense)		(1,346	)		2,791			2,004
Total other income (expense)		(1,225	)		3,357			2,115
Income before taxes		4,136			20,152			16,382
Income tax expense (benefit)		(2,776	)		12,120			6,681
Net income		6,912			8,032			9,701
Redeemable convertible preferred stock dividends		(11,728	)		(11,745	)		(11,745	)
Net loss attributed to common stockholders	$	(4,816	)	$	(3,713	)	$	(2,044	)
Net loss per common share
Basic	$	(0.92	)	$	(0.57	)	$	(0.28	)
Diluted	$	(0.92	)	$	(0.57	)	$	(0.28	)
Weighted average common shares
Basic		5,223,187			6,463,639			7,309,202
Diluted		5,223,187			6,463,639			7,309,202
Unaudited pro forma(1)
Net income per common share
Basic							$	0.28
Diluted							$	0.26
Weighted average common shares
Basic								34,076,858
Diluted								37,740,386

(1) The unaudited pro forma balance sheet gives effect to the conversion of all outstanding shares of our common stock and our redeemable convertible preferred stock into 33,793,123 shares of Class B common stock upon the completion of an initial public offering.

See notes to consolidated financial statements

F-4

KAYAK Software Corporation and Subsidiaries

Consolidated Statements of Changes in Stockholders’ Equity (Deficit)

(In thousands, except share amounts)

	Common Stock						Additional Paid-In Capital			Cumulative Translation Adjustment			Accumulated Deficit			Total Stockholders’ Deficit
	Shares			Amount
Balance, January 1, 2009		5,127,443		$	5		$	—		$	—		$	(22,945	)	$	(22,940	)
Stock option expense		—			—			5,159			—			—			5,159
Issuance of common stock		229,482			—			529			—			—			529
Restricted stock vesting		37,271			—			288			—			—			288
Dividends on preferred stock		—			—			(5,976	)		—			(5,752	)		(11,728	)
Net income		—			—			—			—			6,912			6,912
Balance, December 31, 2009		5,394,196			5			—			—			(21,785	)		(21,780	)
Stock option expense		—			—			8,503			—			—			8,503
Issuance of common stock		1,985,812			2			13,156			—			—			13,158
Excess tax benefits from stock-based compensation		—			—			2,553			—			—			2,553
Dividends on preferred stock		—			—			(11,745	)		—			—			(11,745	)
Foreign currency translation		—			—			—			829			—			829
Net income		—			—			—			—			8,032			8,032
Total comprehensive income																	8,861
Balance, December 31, 2010		7,380,008			7			12,467			829			(13,753	)		(450	)
Stock option expense		—			—			12,427			—			—			12,427
Issuance of common stock		330,678			1			2,124			—			—			2,125
Exercise of put options		(685,219	)		(1	)		(13,220	)		—			—			(13,221	)
Excess tax benefits from stock-based compensation		—			—			1,243			—			—			1,243
Dividends on preferred stock		—			—			(11,745	)		—			—			(11,745	)
Foreign currency translation		—			—			—			(1,806	)		2			(1,804	)
Net income		—			—			—			—			9,701			9,701
Total comprehensive income																	7,897
Balance, December 31, 2011		7,025,467		$	7		$	3,296		$	(977	)	$	(4,050	)	$	(1,724	)

See notes to consolidated financial statements

F-5

KAYAK Software Corporation and Subsidiaries

Consolidated Statements of Cash Flows

(In thousands)

	Year Ended December 31,
	2009			2010			2011
Cash flows from operating activities
Net income	$	6,912		$	8,032		$	9,701
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization		5,380			6,821			8,486
Stock-based compensation expense		5,447			8,503			12,427
Excess tax benefits from exercise of stock options		—			(237	)		(1,441	)
Deferred taxes		(3,925	)		7,418			(12,723	)
Mark to market adjustments		669			(2,792	)		(1,211	)
Loss on extinguishment of debt		1,005			—			—
Gain on sale of TravelPost		—			(459	)		—
Impairment of intangible assets		—			—			14,980
Other		(4	)		47			122
Changes in assets and liabilities, net of effect of acquisitions:
Accounts receivable, net		(2,103	)		(10,794	)		(6,546	)
Prepaid expenses and other current assets		(925	)		(1,238	)		1,555
Accounts payable		1,658			(2,811	)		4,538
Accrued liabilities and other liabilities		(1,498	)		9,442			3,011
Net cash from operating activities		12,616			21,932			32,899
Cash flows from investing activities
Capital expenditures		(2,269	)		(2,273	)		(4,260	)
Proceeds from sale of property and equipment		5			—			42
Purchase of marketable securities		(3,254	)		(6,197	)		(25,644	)
Maturities of marketable securities		12,482			3,276			18,395
Proceeds from sale of TravelPost		—			3,600			—
Exercise of put options		—			—			(13,221	)
Cash paid for business combinations, net of cash acquired		—			(6,781	)		(9,160	)
Net cash from investing activities		6,964			(8,375	)		(33,848	)
Cash flows from financing activities
Proceeds from exercise of stock options		529			464			1,862
Tax benefits realized from exercise of stock options		—			237			1,441
Cash paid for expenses in connection with initial public offering		—			—			(1,494	)
Proceeds from exercise of common stock warrants		—			1,350			—
Payments on long-term debt		(25,268	)		—			—
Loans to shareholders		(2,500	)		—			—
Repayment of shareholder loans		—			3,686			—
Net cash from financing activities		(27,239	)		5,737			1,809
Effect of exchange rate changes on cash and cash equivalents		—			(278	)		(699	)
Increase (decrease) in cash and cash equivalents		(7,659	)		19,016			161
Cash and cash equivalents, beginning of period		23,609			15,950			34,966
Cash and cash equivalents, end of period	$	15,950		$	34,966		$	35,127
Supplemental disclosures of cash flow information
Cash paid during the period for:
Interest	$	532		$	—		$	—
Income taxes	$	2,692		$	1,151		$	16,506

See notes to consolidated financial statements

F-6

KAYAK Software Corporation and Subsidiaries

Notes to Consolidated Financial Statements

(In thousands, except share and per share amounts)

1. Organization

The Company was incorporated in Delaware on January 14, 2004 under the name of Travel Search Company, Inc. On August 17, 2004, we officially changed our name to KAYAK Software Corporation (the Company). We operate KAYAK.com and other travel websites and mobile applications that allow users to search for rates and availability for airline tickets, hotel rooms, rental cars, and other travel-related services across hundreds of websites.

2. Summary of Significant Accounting Policies

Significant Estimates and Judgments

The preparation of financial statements in conformity with generally accepted accounting principles in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates relied upon in preparing these financial statements include the provision for uncollectible accounts, estimates used to determine the fair value of our common stock, put option, stock-based compensation and preferred stock warrants, recoverability of our net deferred tax assets and the fair value of long lived assets and goodwill. Changes in estimates are recorded in the period in which they become known. We base estimates on historical experience and various other assumptions that we believe to be reasonable under the circumstances. Actual results may differ from our estimates.

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, and have been prepared in accordance with accounting principles generally accepted in the United States of America. Operating results of acquired businesses are included in the consolidated statements of operations from the date of acquisition. All intercompany accounts and transactions have been eliminated.

Foreign Currency Translation

Operations outside of the United States generally use their local currency as their functional currency. Assets and liabilities for these operations are translated at exchange rates in effect at the balance sheet date. Income and expense accounts are translated at average exchange rates for the period. Resulting translation adjustments are recorded as a separate component of accumulated other comprehensive income.

Segments

We have one operating segment for financial reporting purposes: travel search.

Revenue Recognition

We generate revenue through display advertisements and when we refer a user to a third-party website, either through our query results or through advertising placements on our websites and by facilitating transactions through our websites and mobile applications. We recognize revenue upon completion of the referral, provided that our fees are fixed and determinable, there is persuasive evidence of the arrangement and collection is reasonably assured, as follows:

Distribution Revenues. Revenues are recognized either when a user clicks on a link that refers them to a third-party provider or when the user completes a purchase with the third party provider, depending on terms of

F-7

the contract. For certain hotels and car rental companies revenue is not earned until the user consumes the travel, in which case we recognize the revenue in the period in which the travel was consumed. Generally, we receive travel consumption reports from travel suppliers and OTAs on a monthly basis which report in detail travel consumed in the immediately prior month.

Advertising Revenues. Revenues are recognized when a user clicks on an advertisement that a customer has placed on our website or when we display an advertisement, regardless of whether the user clicks on the advertisement.

Concentrations of Credit Risk

Substantially all of our revenues are derived from customers and users located in the United States of America. Financial instruments that subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, marketable securities and accounts receivable. The Company’s cash and cash equivalents and marketable securities are primarily held in one financial institution that we believe to be of high credit quality.

Significant customers accounted for the following percentages of total revenues:

	For the year ended December 31,
	2009			2010			2011
Customer A		16	%		25	%		24	%
Customer B		23	%		18	%		12	%
Customer C		13	%		8	%		6	%

Amounts due from these significant customers were:

	At December 31,
	2010		2011
Customer A	$	6,535	$	7,354
Customer B		4,846		4,242
Customer C		740		1,045

We believe significant customer amounts outstanding at December 31, 2011 are collectible.

Cost of Revenues

Cost of revenues consists primarily of expenses incurred related to airfare query costs, data center costs and related bandwidth charges. All costs of revenues are expensed as incurred.

Marketing

Marketing expenses are comprised primarily of costs of search engine marketing, brand advertising, affiliate referral fees, and public relations. All marketing costs are expensed as incurred.

Stock-Based Compensation

We estimate the value of stock option awards on the date of grant using the Black-Scholes option-pricing model (the Black-Scholes model). The determination of the fair value of stock option awards on the date of grant is affected by our estimated stock price as well as assumptions regarding a number of complex and subjective

F-8

variables. These variables include our expected stock price volatility over the term of the awards, expected term, risk-free interest rate, expected dividends and expected forfeiture rates. The forfeiture rate is estimated using historical option cancellation information, adjusted for anticipated changes in exercise and employment termination behavior. We separate employees into groups that have similar characteristics for purposes of making forfeiture estimates. Outstanding awards do not contain market or performance conditions and therefore, we recognize stock-based compensation expense on a straight-line basis over the requisite service period.

Fair Value of Financial Instruments

The carrying amounts of the Company’s cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximate fair value because of their short maturities.

Cash Equivalents and Marketable Securities

Cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase.

Marketable securities are classified as held-to-maturity as we have the intent and ability to hold these investments to maturity. Marketable securities are reported at amortized cost. Cash equivalents and marketable securities are invested in instruments we believe to be of high-quality, primarily money market funds, U.S. Government obligations, State and Municipality obligations and corporate bonds with remaining contractual maturities of less than one year.

Accounts Receivable and Allowance for Doubtful Accounts

We review accounts receivable on a regular basis and estimate an amount of losses for uncollectible accounts based on our historical collections experience, age of the receivable and knowledge of the customer. We record changes in our estimate to the allowance for doubtful accounts through bad debt expense and relieve the allowance when accounts are ultimately determined to be uncollectible.

Deferred Financing Costs Related to Initial Public Offering

As of December 31, 2011 we had incurred $2,173 of legal and accounting costs related to our initial public offering (IPO). We capitalize such costs in prepaid expense and other current assets. Upon successful completion of an IPO these costs will be netted against the proceeds. In the event the IPO is not consummated, such costs will be expensed immediately in general and administrative expenses.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation of property and equipment is computed on a straight-line basis over the estimated useful lives of the assets or, when applicable, the life of the lease, whichever is shorter.

Software and Website Development Costs

Certain costs to develop internal use computer software are capitalized provided these costs are expected to be recoverable. These costs are included in property and equipment and are amortized over three years beginning when the asset is substantially ready for use. Costs incurred during the preliminary project stage, as well as maintenance and training costs are expensed as incurred. We capitalized software and website development costs of $621, $1,363 and $1,020 during the years ended December 31, 2009, 2010 and 2011, respectively. Amortization expense for software and website development costs was $466, $621 and $881 for the years ended December 31, 2009, 2010 and 2011, respectively.

F-9

Impairment of Long-Lived Assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. When such events occur, we compare the carrying amounts of the assets to their undiscounted expected future cash flows. If this comparison indicates that there is impairment, the amount of the impairment is calculated as the difference between the carrying value and fair value. During the year ended December 31, 2011 we recorded an impairment charge of $15.0 million on trade and domain name assets related to our decision to discontinue the sidestep.com URL. See “—Note 6—Intangible Assets” for additional description of our impairment charge.

Goodwill

Goodwill represents the excess of the cost of acquired business over the fair value of the assets acquired at the date of acquisition. Goodwill is tested for impairment at least annually and whenever events or changes in circumstances indicate that goodwill may be impaired. Goodwill is not deductible for tax purposes.

We assess goodwill for possible impairment using a two-step process. The first step identifies if there is potential goodwill impairment. If step one indicates that an impairment may exist, a second step is performed to measure the amount of the goodwill impairment, if any. Goodwill impairment exists when the estimated fair value of goodwill is less than its carrying value. If impairment exists, the carrying value of the goodwill is reduced to fair value through an impairment charge in our consolidated statements of operations.

For purposes of goodwill impairment testing, we estimate the fair value of the company using generally accepted valuation methodologies, including market and income based approaches, and relevant data available through and as of the testing date. The market approach is a valuation method in which fair value is estimated based on observed prices in actual transactions and on asking prices for similar assets. Under the market approach, the valuation process is essentially that of comparison and correlation between the subject asset and other similar assets. The income approach is a method in which fair value is estimated based on the cash flows that an asset could be expected to generate over its useful life, including residual value cash flows. These cash flows are then discounted to their present value using a rate of return that accounts for the relative risk of not realizing the estimated annual cash flows and for the time value of money.

Warrant liability

Warrants to purchase redeemable convertible preferred stock are accounted for on the balance sheets at fair value as liabilities. Changes in fair value are recognized in earnings in the period of change.

Put liability

In connection with our acquisition of swoodoo AG, we issued a put option on 825,000 shares of our common stock. The fair value of this option was estimated to be $4,208 at the date of the acquisition and recorded as a liability on our balance sheet. Changes in fair value were recognized in earnings in the period of change. These options expired on August 12, 2011. See “—Note 3—Acquisitions” for further discussion of the our swoodoo acquisition.

Accumulated Other Comprehensive Income

Accumulated other comprehensive income consists of foreign currency translation adjustments. The financial statements of non-U.S. entities are translated from their functional currencies into U.S. dollars. Assets and liabilities are translated at period end rates of exchange and revenue and expenses are translated using average rates of exchange. The resulting gain or loss is included in accumulated other comprehensive income on the balance sheet.

F-10

Income Taxes

We record income taxes under the liability method. Interest and penalties related to income tax liabilities, if any, are included in income tax expense. Deferred tax assets and liabilities reflect our estimation of the future tax consequences of temporary differences between the carrying amounts of assets and liabilities for book and tax purposes. We determine deferred income taxes based on the differences in accounting methods and timing between financial statement and income tax reporting. Accordingly, we determine the deferred tax asset or liability for each temporary difference based on the enacted tax rates expected to be in effect when we realize the underlying items of income and expense. We consider many factors when assessing the likelihood of future realization of our deferred tax assets, including our recent earnings experience by jurisdiction, expectations of future taxable income, and the carryforward periods available to us for tax reporting purposes, as well as other relevant factors. We may establish a valuation allowance to reduce deferred tax assets to the amount we believe is more likely than not to be realized. Due to inherent complexities arising from the nature of our businesses, future changes in income tax law, tax sharing agreements or variances between our actual and anticipated operating results, we make certain judgments and estimates. Therefore, actual income taxes could materially vary from these estimates.

Effective January 1, 2007, we adopted the authoritative guidance for uncertainty in income taxes. This guidance requires that we recognize a tax benefit from an uncertain position only if it is more likely than not that the position is sustainable, based solely on its technical merits and consideration of the relevant taxing authority’s widely understood administrative practices and precedents. If this threshold is met, we would measure the tax benefit as the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. The adoption of this guidance did not have a material impact on our financial statements. Penalties and interest on uncertain tax positions are included in income tax expense.

Recent Accounting Pronouncements

In 2010, the FASB issued an amendment to guidance on the disclosure of fair value measurements. This update requires a gross presentation of activities within the Level 3 roll forward and adds a new requirement to disclose transfers in and out of Level 1 and 2 measurements. The update also clarifies the following existing disclosure requirements regarding: (i) the level of disaggregation of fair value measurements; and (ii) the disclosures regarding inputs and valuation techniques. This update is effective for our fiscal year beginning January 1, 2010 except for the gross presentation of the Level 3 roll forward information, which was adopted on January 1, 2011. The principle impact from this update was expanded disclosures regarding our fair value measurements.

In May 2011, the FASB issued amendments to fair value measurement guidance to achieve common fair value measurement and disclosure requirements in U.S. GAAP and IFRS. The most significant changes to disclosure requirements are to disclose for recurring Level 3 fair value measurements quantitative information about unobservable inputs used, a description of the valuation process and a qualitative discussion about the sensitivity of measurements. New disclosures are required about the use of a nonfinancial asset measured or disclosed at fair value if its use differs from highest and best use. In addition entities must report the Level in the hierarchy of assets and liabilities not recorded at fair value but where fair value is disclosed. The amendment is effective for our interim and annual periods beginning January 1, 2012. The principle impact will be expanded disclosure.

In December 2010, the FASB issued guidance to clarify the acquisition date that should be used for reporting pro-forma financial information for business combinations. If comparative financial statements are presented, the pro-forma revenue and earnings of the combined entity for the comparable prior reporting period should be reported as though the acquisition date for all business combinations that occurred during the current year had been completed as of the beginning of the comparable prior annual reporting period. This guidance is effective for acquisitions made after December 31, 2010.

F-11

In December 2010, the FASB issued amendments to the guidance on goodwill impairment testing. The amendments modify Step 1 of the goodwill impairment test for reporting units with zero or negative carrying amounts. For those reporting units, an entity is required to perform Step 2 of the goodwill impairment test if it is more likely than not that a goodwill impairment exists. In making that determination, an entity should consider whether there are any adverse qualitative factors indicating that an impairment may exist. The amendments are effective for fiscal years and interim periods beginning January 1, 2011 and are not expected to have a material impact on our consolidated financial statements.

In June 2011, the FASB issued amended disclosure requirements for the presentation of comprehensive income. The amended guidance eliminates the option to present components of other comprehensive income (OCI) as part of the statement of changes in equity. Under the amended guidance, all changes in OCI are to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. The changes are effective January 1, 2012. Early application is permitted. There will be no impact to the consolidated results as the amendments relate only to changes in financial statement presentation.

In September 2011, the FASB issued amended guidance that will simplify how entities test goodwill for impairment. After an assessment of certain qualitative factors, if it is determined to be more likely than not that the fair value of a reporting unit is less than its carrying amount, entities must perform the quantitative analysis of the goodwill impairment test. Otherwise, the quantitative test becomes optional. The guidance is effective January 1, 2012, with early adoption permitted. We elected to adopt this guidance for the 2011 goodwill impairment test performed in the fourth quarter. Goodwill impairment testing did not result in any impact to our financial results.

3. Acquisitions

On May 6, 2010, the Company acquired 100% of the outstanding share capital in swoodoo AG, a leading German travel search company, for a total purchase price of $24,384, consisting of $6,781 in cash, net, and 825,000 shares of common stock valued at $13.00 per share on the date of the acquisition. Pursuant to an option agreed to with the former swoodoo stockholders, we were obligated, at a holder’s request given on or prior to August 12, 2011, to repurchase any or all of such shares owned by such holder at a price of €13.33 per share. We recorded a liability for the estimated fair value of this obligation at $4,208 at the time of acquisition. This amount was recorded as contingent consideration and is included in the purchase price above. The fair value of the obligation decreased by $2,946 and $1,262 for the years ended December 31, 2010 and 2011, respectively. During 2011, $1,126 of the decrease in the liability was recorded as a gain and is included in other income (expense), net. As of August 12, 2011, the expiration date of the option, these holders elected to sell back to the Company an aggregate of 685,219 of these shares. As a result of the exercises of this option, the Company acquired these shares for a cash payment of approximately $13,200.

We recognized $419 of acquisition-related expenses, for the year ended December 31, 2010 that were included in other general and administrative expenses.

The following table summarizes the consideration paid for swoodoo AG and the amounts of the assets acquired and liabilities assumed at the acquisition date.

Fair value of consideration transferred:

Cash paid	$	8,777
Cash paid for working capital adjustment		674
Fair value of common stock		10,725
Fair value of put options issued		4,208
Total purchase consideration	$	24,384

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The table below sets forth the final purchase price allocation.

Assets acquired:
Cash and cash equivalents	$	2,670
Other assets		1,320
Identifiable intangible assets (1)
Customer relationships (useful life - 8 years)		4,900
Trade & domain names (useful life - 11 years)		5,400
Current technology (useful life - 5 years)		3,900
Non-compete agreements (useful life - 3 years)		700
Goodwill		11,144
Total assets		30,034
Liabilities assumed:
Deferred tax liability		4,714
Other liabilities		936
Total net assets acquired	$	24,384

⁽¹⁾ The weighted average useful life of the identifiable intangible assets acquired is 8 years.

The primary elements that generated goodwill are the value of the acquired assembled workforce, specialized processes and procedures and operating synergies, none of which qualify as separate intangible asset.

The pro forma impact of this acquisition on revenues and net income was immaterial.

On April 1, 2011, the Company acquired 100% of the outstanding share capital in JaBo Vertrieb-und Entwicklung GmbH, or JaBo Software, a leading Austrian travel search company, for a total cash purchase price of $9,160, net.

The table below sets forth the final purchase price allocation:

Assets acquired:
Accounts receivable and other assets	$	983
Contingent asset		230
Identifiable intangible assets (1)
Customer relationships (useful life—7 years)		3,200
Trade & domain names (useful life—10 years)		2,600
Current technology (useful life—2 years)		700
Non-compete agreements (useful life—2 years)		300
Goodwill		4,138
Total assets		12,151
Liabilities assumed:
Deferred tax liability		1,700
Other liabilities		1,291
Total net assets acquired	$	9,160

⁽¹⁾  The weighted average useful life of the identifiable intangible assets acquired is 7 years.

The primary elements that generated goodwill are the value of the acquired assembled workforce, specialized processes and procedures and operating synergies, none of which qualify as separate intangible assets.

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The pro forma impact of this acquisition on revenues and net income was immaterial.

4. Marketable Securities

The following tables summarize the investments in marketable securities all of which are classified as held to maturity:

	December 31, 2010				December 31, 2011
	Amortized Cost		Level  1(1) Fair Value		Amortized Cost		Level  1(1) Fair Value
Agency bonds	$	737	$	737	$	2,605	$	2,605
Agency discount notes		750		750		—		—
U.S. government bonds		200		200		—		—
Non-U.S. government bonds		125		125		—		—
Certificate of deposit		—		—		900		899
Commercial paper		1,050		1,050		3,097		3,096
Corporate debentures/ bonds		1,500		1,500		4,596		4,591
Marketable securities	$	4,362	$	4,362	$	11,198	$	11,191

⁽¹⁾  Level 1 fair values are defined as observable inputs such as quoted prices in active markets.

5. Property and Equipment

Property and equipment consisted of the following:

	Estimated Life	December 31,
		2010			2011
Website development	3 years	$	6,795		$	5,552
Computer equipment	3 years		2,962			4,172
Leasehold improvements	Life of lease		993			2,283
Furniture and fixtures	5 years		419			749
Software	3 years		140			266
Vehicles	5 years		105			53
Office equipment	5 years		35			40
Property and equipment			11,449			13,115
Accumulated depreciation			(8,015	)		(7,641	)
Property and equipment, net		$	3,434		$	5,474

Depreciation expense was $2,052, $2,202, and $1,920 for the years ended December 31, 2009, 2010 and 2011, respectively.

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6. Intangible Assets

The following tables detail our intangible asset balances by major asset class:

	December 31, 2010							December 31, 2011
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Impairment			Net Carrying Amount
Intangible asset class
Domain and trade names	$	31,144	$	(8,230	)	$	22,914	$	33,505	$	(11,255	)	$	(14,980	)	$	7,270
Customer relationships		8,073		(2,347	)		5,726		10,878		(3,826	)		—			7,052
Technology		4,037		(525	)		3,512		4,160		(1,287	)		—			2,873
Non-compete agreements		725		(158	)		567		982		(493	)		—			489
Intangible assets, net	$	43,979	$	(11,260	)	$	32,719	$	49,525	$	(16,861	)	$	(14,980	)	$	17,684

Amortization expense was $3,328, $4,619 and $6,566 for the years ended December 31, 2009, 2010 and 2011, respectively. Intangible assets are amortized on a straight-line basis over their estimated economic lives. We believe that the straight-line method of amortization reflects an appropriate allocation of the cost of the intangible assets to earnings in proportion to the amount of economic benefits obtained.

In January 2011, we determined that we would not support two brand names and URLs in the United States and decided that we would begin to migrate all traffic from sidestep.com to KAYAK.com. As a result of this triggering event, we prepared an analysis comparing expected future discounted cash flows to be generated by the SideStep domain and tradename asset to the carrying value of the asset. Our analysis resulted in:

• A charge of $14,980 due to the impairment of the value of the SideStep brand name and URL,

• A change in estimate that resulted in acceleration of amortization based on the estimated decline in queries directed from our SideStep URL through December 2013 to reflect the gradual transition of users to the KAYAK URL.

To determine fair value, we used an income approach, which utilized Level 3 fair value inputs as discussed below, and discounted the expected cash flows of the intangible assets. We calculated expected cash flows, using an estimate of future revenue to be generated from the SideStep URL offset by estimated future expenses. We applied a discount rate of 17% representing the estimated weighted average cost of capital, which reflects the overall level of inherent risk involved in the respective operations and the rate of return an outside investor could expect to earn.

As of December 31, 2011, future amortization expense for the next 5 years and after is expected to be:

2012	$	5,185
2013		2,513
2014		1,863
2015		1,849
2016		1,849
Thereafter		4,425
Total	$	17,684

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7. Goodwill

Changes in the carrying amount of goodwill for the years ended December 31, 2010 and 2011 were as follows:

Balance, December 31, 2009	$	142,982
Acquisition of swoodoo AG		11,144
Sale of TravelPost, Inc.		(2,353	)
Foreign currency translation		391
Balance, December 31, 2010		152,164
Acquisition of JaBo Software		4,138
Foreign currency translation		(625	)
Balance, December 31, 2011	$	155,677

8. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:

	December 31,
	2010		2011
Accrued bonus	$	3,750	$	5,792
Income taxes payable		4,544		2,515
Accrued search fees		1,894		1,243
Accrued marketing		1,842		1,141
Other accrued expenses		2,903		5,529
Accrued expenses and other current liabilities	$	14,933	$	16,220

9. Income Taxes

Domestic pre-tax income was $4,044, $20,636, and $11,803 for the years ended December 31, 2009, 2010 and 2011, respectively. Foreign pre-tax income (loss) was $92, $(484) and $4,579 for the years ended December 31, 2009, 2010 and 2011 respectively.

The significant components of the provision for income taxes are as follows:

	December 31,
	2009			2010			2011
Current:
Federal	$	141		$	3,648		$	12,665
State		1,008			3,576			3,864
Foreign		—			146			2,844
Total current		1,149			7,370			19,373
Deferred
Federal		(3,098	)		3,844			(9,454	)
State		(827	)		1,115			(1,495	)
Foreign		—			(209	)		(1,743	)
Total deferred		(3,925	)		4,750			(12,692	)
Income tax expense (benefit)	$	(2,776	)	$	12,120		$	6,681

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Provisions for income taxes compared with income taxes based on the federal statutory tax rate of 35% were as follows:

	December 31,
	2009			2010			2011
U.S. Statutory federal income tax rate		35.0	%		35.0	%		35.0	%
State income taxes, net of federal benefits		15.8	%		8.3	%		7.2	%
Compensation related to incentive stock options		27.0	%		7.1	%		6.0	%
Gain on sale of TravelPost		—			4.4	%		—	%
Mark-to-market adjustments		5.7	%		(4.8	)%		(2.6	)%
Change to valuation allowance		(149.1	)%		8.0	%		—	%
Foreign Rate Differential		—			—			(2.7	)%
Other		(1.5	)%		2.1	%		(2.1	)%
Effective income tax rate		(67.1	)%		60.1	%		40.8	%

Significant components of deferred tax assets and (liabilities) at December 31, 2010 and 2011 were as follows:

	December 31,
	2010			2011
Deferred tax assets:
Net operating loss carryforward	$	4,780		$	4,037
Accruals and reserves		849			1,633
Stock compensation		2,977			6,431
Tax credits		—			21
Total gross deferred tax assets		8,606			12,122
Valuation allowance		(1,617	)		(1,627	)
Total deferred tax assets		6,989			10,495
Deferred tax liabilities:
Depreciation and amortization		(12,474	)		(4,997	)
Net deferred tax asset (liability)	$	(5,485	)	$	5,498

At December 31, 2011, we had approximately $6,038 and $33,872 of federal and state tax NOLs, respectively, that expire beginning in 2021 and 2015, respectively. This includes the effect of Section 382 limitations on our federal NOL due to certain ownership changes in prior years. We had approximately $464 of tax credits at December 31, 2010 which are not included in the above deferred tax schedule. The credits were fully utilized in 2011 and the tax benefit was recorded in additional paid in capital.

During the year ended December 31, 2010, we recorded a valuation allowance against our California net operating losses and credits. The decision to record this valuation allowance was based on our decision to reduce our physical presence in California. It is therefore more likely than not that these losses and credits will expire without being utilized against future taxable income. There was no significant change to our valuation allowance during 2011.

We have not recorded U.S. income and foreign withholding tax liabilities on the unremitted earnings of our foreign subsidiaries, because we intend to permanently reinvest those earnings. The amount of unremitted earnings at December 31, 2011, for which U.S. income and foreign withholding tax liabilities have not been provided, is approximately $3,600. At this time, determination of the amount of unrecognized tax liabilities is not practicable.

F-17

The following table summarizes the changes in the balance of gross unrecognized tax benefits for the years ended December 31, 2009, 2010 and 2011:

Unrecognized tax benefits at January 1, 2009	$	—
Additions for 2009		231
Unrecognized tax benefits at December 31, 2009		231
Additions for 2010		282
Unrecognized tax benefits at December 31, 2010		513
Additions for 2011		327
Unrecognized tax benefits at December 31, 2011	$	840

All of the unrecognized tax benefits, if recognized, would impact our effective tax rate. The Company does not currently anticipate that the total amount of unrecognized tax benefits will significantly change within the next 12 months.

All years are open for examination by federal and state taxing authorities. The Commonwealth of Massachusetts commenced an audit of our 2007 and 2008 income tax returns during the first quarter of 2011. We believe we have adequately reserved for all uncertain tax positions. Our assessment relies on estimates and assumptions and a series of complex judgments about future events.

10. Commitments and Contingencies

Operating Leases

We lease our office and data center facilities under noncancelable leases that expire at various points through August 2017. We are also responsible for certain real estate taxes, utilities and maintenance costs on our office facilities. Rent expense was approximately $1,307, $1,070 and $1,746 for the years ended December 31, 2009, 2010 and 2011, respectively. Future minimum payments under non cancelable operating lease agreements as of December 31, 2011 are as follows:

2012	$	1,697
2013		1,164
2014		1,064
2015		979
2016		862
Thereafter		535
Total	$	6,301

Other Commitments

In addition, we have a content licensing agreement that as of December 31, 2011, obligates us to make minimum future payments of $7,000 in 2012. During 2013, we will be obligated to make minimum payments based on the number of queries performed in 2012, and as a result, we are unable to estimate our calendar year 2013 minimum commitment at this time. If not renewed, this agreement expires in December 2013.

Legal Matters

We are involved in various legal proceedings, including but not limited to the matters described below that involve claims for substantial amounts of money or for other relief or that might necessitate changes to our business or operations.

F-18

In April 2009, Parallel Networks, LLC filed a complaint against us for patent infringement in the U.S. District Court for the Eastern District of Texas. The complaint alleged, among other things, that our website technology infringes a patent owned by Parallel Networks purporting to cover a “Method And Apparatus For Client-Server Communication Using a Limited Capability Client Over A Low-Speed Communications Link” (U.S. Patent No. 6,446,111 B1) and sought injunctive relief, monetary damages, costs and attorneys fees. The complaint was dismissed without prejudice in February 2010, but the plaintiff filed a new complaint against us on March 29, 2010 containing similar allegations. The case was set for trial on September 10, 2012. The court has since stayed proceedings in the district court pending resolution of plaintiff’s appeal of certain rulings by the court, which granted summary judgment on several claims in favor of us and other defendants.

In August 2010, Orbitz initiated arbitration with us through the American Arbitration Association in the state of New York. Orbitz contends that we violated the parties’ 2009 Promotion Agreement by failing to abide by certain exclusivity provisions relating to the display of certain advertising placements on our websites. It also contends that we owe it in excess of $2,500 as a result of “net revenue” overpayments that Orbitz allegedly made to us over the past few years when Orbitz calculated and reported its own net revenue obligations under the agreement. We denied Orbitz’s allegations and asserted a number of affirmative defenses in response to both claims. A three-day evidentiary hearing took place in New York on May 24, 2011. On December 31, 2011, the arbitration panel issued an interim order that, with limited exceptions, found in our favor regarding the exclusivity provisions of the agreement. On the “net revenue claim,” the arbitration panel ordered the parties to engage in an audit which was pending as of year end.

On March 22, 2011, Orbitz filed a lawsuit against us in the Circuit Court of Cook County in Chicago, Illinois alleging that we violated the 2009 Promotion Agreement by failing to abide by certain exclusivity provisions because of our use of certain third party technology providers in connection with our hotel booking functionality. Orbitz sought a temporary restraining order to restrain our use of this booking feature. On March 25, 2011, the judge denied Orbitz’s request for a temporary restraining order, finding that Orbitz did not sustain its burden of showing a likelihood of success on the merits. On May 9, 2011, Orbitz initiated an arbitration asserting these same claims. On May 11, 2011, Orbitz voluntarily dismissed the court case in favor of continuing to arbitrate the matter. The parties are now in the process of finalizing the designation of the arbitration panel. No other deadlines have been set. We intend to vigorously defend ourselves in this matter.

On June 13, 2011, Source Search Technologies LLC filed a complaint against us for patent infringement in the U.S. District Court of New Jersey. The complaint alleges, among other things, that our website infringes a patent owned by Source Search entitled, a “Computerized Quotation System and Method.” According to the complaint, the patent allegedly allows a central computer to filter requests for quotes, and to interface to various vendor computers to obtain and forward these quotes to potential buyers of goods and services. We were served with the complaint on June 17, 2011. We filed a response on August 5, 2011, denying the allegations of patent infringement and asserting a counterclaim for declaratory judgment of non-infringement and invalidity. On November 3, 2011, the court terminated the case, pending the conclusion of the U.S. Patent Office’s reexamination of Source Search’s patent.

On September 15, 2011, LVL Patent Group, LLC (now known as CyberFone Systems, LLC, or CyberFone) filed a complaint against us for patent infringement in the U.S. District Court for the District of Delaware. The complaint alleges, among other things, that our technology infringes a patent owned by CyberFone purporting to cover a “Telephone/Transaction Entry Device and System for Entering Transaction Data in Databases” and seeks injunctive relief, monetary damages, costs and attorneys fees. More specifically, the complaint alleges infringement by providers who make, use, sell, offer to sell, or import a method of obtaining data transaction information entered on a telephone, forming a plurality of exploded data transactions for the single transaction, and sending different exploded data transactions to different destinations, using its mobile services network platform. We intend to vigorously defend ourselves in this matter.

F-19

On December 29, 2011, Data Distribution Technologies LLC, or DDT, filed a complaint against us for patent infringement in the U.S. District Court for the Southern District of New York. The complaint alleges, among other things, that our website infringes a patent owned by DDT entitled, a “Web-Updated Database with Record Distribution by Email.” According to the complaint, the patent covers a system for maintaining, updating and distributing by email flight information records corresponding to desired flights on a subscribing traveler’s “Price Alerts” list, and a method of maintaining, updating and distributing by email flight information records to travelers. We were served with the complaint on January 11, 2012.

In addition, from time to time, we may become involved in legal proceedings arising in the ordinary course of our business. Such proceedings, even if not meritorious, could result in the expenditure of significant financial and managerial resources. If any legal proceedings were to result in an unfavorable outcome, it could have a material adverse effect on our business, financial position and results of operations; however, at this time, we are unable to estimate the potential range of loss, if any, and it is too early to determine the likelihood of whether or not any of these claims will ultimately result in a loss. As such, we have not recorded any accrual for potential loss as of December 31, 2010 or December 31, 2011.

11. Redeemable Convertible Preferred Stock

The Company has authorized 26,876,384 shares of redeemable convertible preferred stock, and has designated six series as of December 31, 2011: 6,600,000 shares of Series A Preferred, 1,176,051 shares of Series A-1 Preferred, 4,989,308 shares of Series B Preferred, 2,138,275 shares of Series B-1 Preferred, 3,897,084 shares of Series C Preferred and 8,075,666 Series D Preferred.

Series A Preferred

In March and June 2004, the Company issued an aggregate of 6,600,000 shares of Series A Preferred at $1.00 per share for gross proceeds of $6,600.

Series A-1 Preferred

In November 2004, the Company issued an aggregate of 825,000 shares of Series A-1 Preferred at $2.00 per share for gross proceeds of $1,650. The purchase price of the shares was subject to adjustment based on any dilution occurring as a result of any subsequent stock offering that occurred prior to February 1, 2006 at a price per share lower than $2.00. Consequently, in March 2005, an additional 351,051 shares were issued to Series A-1 holders to adjust the stock purchase price to $1.403 per share, the per-share price of the Series B Preferred Stock.

Series B Preferred

In February 2005, the Company issued 4,989,308 shares of its Series B Preferred at $1.403 per share for gross proceeds of $7,000.

Series B-1 Preferred

In April 2006, the Company issued 2,138,275 shares of its Series B-1 Preferred at $1.403 per share for gross proceeds of $3,000.

Series C Preferred

In May 2006, the Company issued 3,855,180 shares of its Series C Preferred at $2.983 per share for gross proceeds of $11,500.

F-20

Series D Preferred

In December 2007, the Company issued 8,008,842 shares of its Series D Preferred at $20.727 per share for gross proceeds of $166,000 and $278 in issuance costs.

A summary of the current rights and preferences of the Series A, A-1, B, B-1, C and D Preferred are as follows:

Voting

Series A, A-1, B, B-1, C and D Preferred stockholders are entitled to one vote per common share equivalent on all matters voted on by holders of common stock.

Dividends

Series A, A-1, B, B-1, C and D Preferred stockholders are entitled to receive dividends that are paid on common stock of the Company equal to an amount of the largest number of whole shares of common stock into which the shares of preferred stock are convertible. In addition, Series A, A-1, B, B-1, C and D preferred stockholders are entitled to receive, out of funds legally available, dividends at the rate of 6% per annum of the adjusted original issue price per share and are accumulated regardless if declared. Accumulated and unpaid dividends totaled $40,000 and $51,745 at December 31, 2010 and 2011 respectively. Dividends are payable upon a liquidation event, redemption or if declared by the Board of Directors.

Liquidation Rights

In the event of a liquidation, dissolution or winding up of the Company, a sale of all or substantially all of the Company’s assets, and certain mergers, before any distribution payments to common stockholders, the holders of Series A, A-1, B, B-1, C and D Preferred are entitled to an amount equal to the liquidation preference payment. The liquidation preference payment is equal to the original stock price paid per share multiplied by 1.5 for the Series A holders ($1.50 per share), Series A-1 holders ($2.104 per share), Series B holders ($2.104 per share), Series B-1 holders ($2.104 per share), Series C holders ($4.475 per share) and Series D holders ($31.09 per share) plus unpaid dividends (whether or not declared).

Conversion

Each share of Series A, A-1, B, B-1, C and D preferred is convertible into one share of common stock, adjusted for certain anti-dilutive events. Conversion is at the option of the holder but becomes automatic upon (i) the completion of an initial public offering involving gross proceeds of at least $25,000 at a price per share that equals or exceeds $31.09 per share, subject to certain adjustments, or (ii) upon the election of the holders of shares of preferred stock representing 58% of the votes applicable to such preferred stock (Requisite Holders), provided that with respect to Series D Preferred, such election must also include holders of at least two-thirds of the Series D preferred. Upon a conversion event holders are not entitled to receive any previously accumulated and unpaid dividends.

Redemption

At any time on or after December 21, 2012, upon the written request of the Requisite Holders, the Company shall redeem, in three equal annual installments, all outstanding Series A, A-1, B, B-1, C and D Preferred, in cash, at an amount equal to the adjusted original issue price plus unpaid dividends. In February 2012, we obtained waivers from more than the Requisite Holders agreeing not to elect any such redemption until after January 2, 2013.

Preferred Stock Warrants

In connection with the issuance of subordinated term loans in 2007, the lender received warrants to purchase 62,000 shares of Series D preferred stock at an exercise price of $20.73 per share. The warrants expire on the

F-21

tenth anniversary of the loan closing date (December 2017). In connection with the transaction the Company recorded a separate warrant liability based on the estimated fair value at the issuance date by allocating proceeds first to the warrants and the remaining to the loans (the residual method). Warrants are valued at each reporting period with changes recorded as other income (expense) in the statement of operations. The fair value of these warrants was $610 and $426 as of December 31, 2010 and 2011, respectively, based on the following assumptions using the Black-Scholes model:

	December 31,
	2010			2011
Risk free interest rate		1.5	%		0.4	%
Expected volatility		47.9	%		42.9	%
Expected life (in years)		4			3
Dividend yield		0.0	%		0.0	%

The mark-to-market gain (loss) on these warrants was $(384), $71 and $183 for the years ended December 31, 2009, 2010 and 2011 respectively.

In November 2006, under the terms of a loan and security agreement, the Company issued warrants for the purchase of 41,904 shares of Series C preferred. The warrants are exercisable at $2.983 per share and expire on November 22, 2016. The Company recorded a warrant liability based on the fair value of the warrants at the issuance date. The fair value of these warrants was $625 and $724 as of December 31, 2010 and 2011, respectively, based on the following assumptions using the Black-Scholes model:

	December 31,
	2010			2011
Risk free interest rate		1.0	%		0.3	%
Expected volatility		48.0	%		41.0	%
Expected life (in years)		3			2
Dividend yield		0.0	%		0.0	%

The mark-to-market gain (loss) on these warrants was $(285), $(226) and $(98) for the years ended December 31, 2009, 2010 and 2011, respectively.

12. Stockholders’ Equity

Common Stock

A summary of the current rights and preferences of common stock are as follows:

Voting

Common stockholders are entitled to one vote per share of common stock held on all matters on which such common stockholder is entitled to vote.

Dividends

Common stockholders are eligible to receive dividends on common stock held when funds are available and as approved by the Board of Directors.

Liquidation Rights

In the event of liquidation, dissolution or winding up of the Company, a sale of all or substantially all of the Company’s assets, and certain mergers, common stockholders are entitled to receive all assets of the Company available for distribution, subject to the preferential rights of any outstanding shares of preferred stock.

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13. Stock Options and Restricted Stock

The Board of Directors adopted the 2004 Stock Option Plan (Plan) and the Third Amended and Restated 2005 Equity Incentive Plan, which permits the sale or award of restricted common stock or grant of incentive and nonqualified stock options for the purchase of common stock to employees, directors and consultants up to a maximum of 2,180,000 shares under the Plan and up to 9,820,000 shares under the Third Amended and Restated 2005 Equity Incentive Plan. At December 31, 2011, 159,946 shares were available under the Third Amended and Restated 2005 Equity Incentive Plan for future issuances of restricted common stock or grants of stock options.

Restricted Stock

The Company has issued shares of restricted common stock to employees, directors and consultants, which are subject to repurchase agreements and generally either vest over a four-year period from date of grant or immediately at the time of the grant. If the holder ceases to have a business relationship with the Company, the Company may repurchase any unvested shares of restricted common stock held by these individuals at their original purchase price. There were no unvested shares at December 31, 2011.

Restricted stock is subject to transfer restrictions and contains the same rights and privileges as unrestricted shares of common stock. Shares of restricted stock are presented as outstanding as of the date of issuance. Grants made during 2010 and 2011 all vested immediately as of the date of the grant.

The following table summarizes the activity for our restricted stock:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2009		345		$	1.40
Granted		54,986			11.29
Vested		(55,331	)		11.23
Unvested at December 31, 2010		—			—
Granted		14,905			17.60
Vested		(14,905	)		17.60
Unvested at December 31, 2011		—		$	—

Stock Options

Stock options generally have terms of ten years. Stock options granted under the stock plans will typically vest 25% after the first year of service and ratably each month over the remaining 36-month period contingent upon employment with the Company on the date of vesting.

The Company utilizes the Black-Scholes model to determine the fair value of stock options. Management is required to make certain assumptions with respect to selected model inputs, including anticipated changes in the underlying stock price (i.e., expected volatility) and option exercise activity (i.e., expected term). The Company bases its expected volatility on the historical volatility of comparable publicly traded companies for a period that is equal to the expected term of the options. We generally use the same group of comparable companies for all valuations, except that when calculating volatility, we exclude any companies in the set that have been public for fewer than two years. The expected term of options granted is derived using the “simplified” method as allowed under the provisions of the Securities and Exchange Commission’s Staff Accounting Bulletin No. 107 and represents the period of time that options granted are expected to be outstanding. The risk-free rate is based on the U.S. Treasury yield in effect at the time of the grant period for a period commensurate with the estimated expected life.

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The following table summarizes stock option activity:

	Number of Shares			Weighted-Average Exercise Price		Aggregate Intrinsic Value(1)		Weighted-Average Remaining Contractual Term (in years)
Balance at December 31, 2010		9,288,901		$	9.40	$	76,183		8.1
Options granted		1,155,000		$	21.60
Exercised		(315,773	)	$	8.22
Canceled/ forfeited		(1,041,542	)	$	11.14
Balance at December 31, 2011		9,086,586		$	10.79	$	86,590		7.3
Vested and exercisable as of December 31, 2011		5,006,494		$	7.20	$	64,788		6.2
Vested and exercisable as of December 31, 2011 and expected to vest thereafter(2)		8,344,545		$	10.32	$	83,242		7.2

(1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying award and the fair value of $17.60 of our common stock on December 31, 2010 and the fair value of $20.14 of our common stock on December 31, 2011.

(2) Stock options expected to vest reflect an estimated forfeiture rate.

The fair value of vested shares was $2,689, $5,770 and $10,885 during the years ended December 31, 2009, 2010 and 2011, respectively. The total intrinsic value of options exercised was $1,597 and $4,143 during the years ended December 31, 2010 and 2011, respectively.

The weighted-average fair value of options granted during the years ended December 31, 2009, 2010 and 2011 was $4.21, $8.03 and $9.71 per share, respectively, based on the Black-Scholes model. The following weighted-average assumptions were used for grants:

	December 31,
	2009			2010			2011
Risk-free interest rate		2.5	%		2.0	%		1.8	%
Expected volatility		57.4	%		47.1	%		43.8	%
Expected life (in years)		6			6			6
Dividend yield		0.0	%		0.0	%		0.0	%

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The following table summarizes information concerning outstanding and exercisable options as of December 31, 2011:

	Options Outstanding						Options Exercisable and Vested
Range of Exercise Prices	Number of Shares		Weighted Average Remaining Contractual Life (in Years)		Weighted- Average Exercise Price		Number of Shares		Weighted- Average Exercise Price
$  1.00 - $  1.40		971,103		2.9	$	1.16		971,103	$	1.16
$  2.98		216,240		4.7	$	2.98		216,240	$	2.98
$  5.00		1,362,500		5.4	$	5.00		1,362,500	$	5.00
$  7.50		1,742,415		7.5	$	7.50		1,072,988	$	7.50
$11.29		257,500		8.0	$	11.29		136,666	$	11.29
$13.00		1,030,000		8.3	$	13.00		454,472	$	13.00
$14.82		1,956,828		8.7	$	14.82		621,383	$	14.82
$15.50 - $21.00		1,355,000		9.2	$	19.28		171,142	$	16.08
$25.50		195,000		9.7	$	25.50		—		—
$  1.00 - $25.50		9,086,586		7.3	$	10.79		5,006,494	$	7.20

The fair value of the common stock has been determined by the Board of Directors at each award grant date based on a variety of factors, including arm’s length sales of the Company’s capital stock (including redeemable convertible preferred stock), valuations of comparable public companies, the Company’s financial position and historical financial performance, the status of technological developments within the Company’s products, the composition and ability of the technology and management team, an evaluation of and benchmark to the Company’s competition, the current climate in the marketplace, the illiquid nature of the common stock, the effect of rights and preferences of preferred shareholders, and the prospects of a liquidity event, among others. In addition, at least annually the Company obtains an independent third party valuation to assist in determining the current market value of the stock.

In 2009, the Company offered employees the ability to modify their stock options that were previously granted at an exercise price in excess of the valuation that was obtained at December 31, 2008. In return for adjusting the fair market value of the options, the vesting on the awards would reset as of July 7, 2009. Employees would then vest in equal monthly installments over the next four years. 2,044,000 options relating to 49 employees were reset at July 7, 2009 with an exercise price of $7.50. In connection with this modification, the Company incurred additional non-cash compensation expense of $2,565 for the incremental value of the modified options. This expense is being recognized on a straight-line basis over the vesting period of the new grant.

At December 31, 2010 and December 31, 2011, total unrecognized estimated compensation expense related to non-vested stock options granted prior to that date was approximately $38,250 and $31,124, respectively. This expense will be recognized on a straight-line basis over the weighted average remaining vesting period of 3.1 years as of December 31, 2010 and 2.6 years as of December 31, 2011.

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14. Earnings per share

The following table sets forth the computation of basic and diluted earnings per share of common stock for the years ended December 31, 2009, 2010 and 2011, were as follows:

	Year ended December 31,
	2009			2010			2011
Basic and diluted earnings per share:
Net income	$	6,912		$	8,032		$	9,701
Redeemable convertible preferred stock dividends		(11,728	)		(11,745	)		(11,745	)
Net (loss) attributable to common stockholders—basic and diluted	$	(4,816	)	$	(3,713	)	$	(2,044	)
Weighted average common shares outstanding		5,223,187			6,463,639			7,309,202
Basic and diluted (loss) per share	$	(0.92	)	$	(0.57	)	$	(0.28	)

The weighted average effect of potentially dilutive securities that have been excluded from the calculation of diluted net loss per common share because the effect is anti-dilutive is as follows:

	Year ended December 31,
	2009		2010		2011
Options to purchase common stock		5,704,576		9,288,901		9,086,586
Common stock subject to repurchase		—		192,783		—
Convertible preferred stock (as converted basis)		26,767,656		26,767,656		26,767,656
Convertible preferred stock warrants (as converted basis)		103,904		103,904		103,904
		32,576,136		36,353,244		35,958,146

Unaudited Pro Forma Net Income (Loss) Per Share

The following table sets forth the computation of basic and diluted earnings per share of common stock assuming that all outstanding shares of common stock and our redeemable convertible preferred stock are converted into 33,793,123 shares of Class B common stock at January 1, 2011:

	December 31, 2011
Pro forma basic earnings per share:
Net income	$	9,701
Weighted average common shares outstanding		7,309,202
Pro forma adjustment for redeemable convertible preferred stock		26,767,656
Weighted average shares outstanding used to compute basic pro forma earnings		34,076,858
Pro forma basic earnings per share	$	0.28
Pro forma diluted earnings per share:
Net income	$	9,701
Weighted average shares outstanding used to compute basic pro forma earnings or loss per share		34,076,858
Options to purchase common stock		3,624,877
Warrants to purchase common stock		38,651
Weighted average shares outstanding used to compute diluted pro forma earnings per share		37,740,386
Pro forma diluted earnings per share	$	0.26

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The weighted average effect of potentially dilutive securities that have been excluded from the calculation of pro forma diluted net income (loss) per common share because the effect is anti-dilutive is as follows:

Options to purchase common stock	5,461,709
Convertible preferred stock warrants (as converted basis)	65,253
Common stock subject to repurchase	—
	5,526,962

15. Fair Value Measurements

Generally accepted accounting principles set forth a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. The three tiers are Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions.

Our preferred stock warrants and common stock put options are measured at fair value on a recurring basis. The preferred stock warrants are valued using the Black-Scholes model with the following assumptions: share price, exercise price, expected term, volatility, risk-free interest rate and dividend yield as described in “—Note 11—Redeemable Convertible Preferred Stock”.

Using the Black-Scholes model, the common stock put options were valued at $1,262 based on the following assumptions at December 31, 2010. As of December 31, 2011, there were no outstanding put options. See “—Note 3—Acquisitions” for further discussion of our swoodoo acquisition and the exercise of the put options.

	December  31, 2010
Risk free interest rate		0.2	%
Expected volatility		31.0	%
Expected life (in years)		0.5
Dividend yield		0.0	%

Changes in valuation during the years ended December 31, 2009, 2010 and 2011, were as follows:

	Level 3 Stock Put Options			Level 3 Warrant Instruments
Balance, December 31, 2009		—			1,081
Fair value at issuance		4,208			—
Mark-to-market adjustment		(2,946	)		154
Balance, December 31, 2010		1,262			1,235
Mark-to-market adjustment		(1,126	)		(85	)
Liquidation of put options		(136	)		—
Balance, December 31, 2011	$	—		$	1,150

Mark-to-market adjustments related to stock put options and warrant instruments are included in other income (expense).

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16. Employee Benefit Plan

In June 2004, the Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis, subject to legal limitations. Company contributions to the plan may be made at the discretion of the Board of Directors. In March 2011, the Company implemented a program that matched a portion of employee 401(k) contributions. For the year ended December 31, 2011, the Company has contributed $399 to the plan.

17. Related Party Transactions

In March 2010, we sold TravelPost, a website that was acquired in 2007, to a corporation affiliated with certain members of our Board of Directors. In return, we received 800,000 shares of common stock in the new company and $3,600 in cash. We recorded a gain on the sale of $459 which is included in other income (expense), net. In addition we entered into a commercial agreement pursuant to which we granted the new company a three-year license to reproduce and publicly display hotel reviews and hotel related information in exchange for a monthly license fee of $50 for the term of the license. In May 2011, the commercial agreement was amended to lower the monthly license fee to $10 in exchange for 1,000,000 shares of Series A Preferred Stock in TravelPost. No value was attributed to the stock.

18. Information about Geographic Areas

Revenues by geography are based on the country in which our websites are located. For example, KAYAK.com is in the United States, while de.KAYAK.com and swoodoo.com are in Germany. We allocate revenues based on the website’s proportional revenue-generating activity (generally, volume of queries and clicks relative to the whole). Long-lived assets are allocated based on the location of the corporate entity to which they relate.

	Year Ended December 31,
	2009		2010		2011
Revenues
United States	$	105,184	$	154,682	$	184,445
Germany		1,272		8,231		24,002
Rest of the world		6,242		7,785		16,087
Total revenues	$	112,698	$	170,698	$	224,534

	As of December 31,
	2010		2011
Long-lived assets
United States	$	162,785	$	149,254
Germany		25,532		20,205
Rest of the world		—		9,376
Total long-lived assets	$	188,317	$	178,835

19. Subsequent Events (unaudited)

We evaluated subsequent events through April 19, 2012, with respect to the consolidated financial statements for the year ended December 31, 2011 and none had a material impact on the financial results.

Willard H. Smith’s employment with us as Chief Financial Officer ended on March 16, 2012, and Melissa H. Reiter was named Chief Financial Officer at that time. As part of his separation we agreed to pay Mr. Smith a

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lump sum amount of $261, representing six months salary and bonus. In addition, we accelerated the vesting of Mr. Smith’s stock option with respect to 50 shares of our common stock.

In connection with our Orbitz arbitration, the audit firm engaged by the parties provided its report in March 2012, which included 4 possible scenarios, all of which found that Orbitz underpaid KAYAK for 2008 and 2009 in varying amounts, between $49 and $2,850. The parties are currently briefing the net revenues issue, as discussed in “Note 10—Commitments and Contingencies—Legal Matters” above, and will engage in limited discovery on damages followed by additional briefing thereafter. We expect a final decision by the arbitration panel after the briefing and discovery is completed.

In April 2012, we entered into a settlement agreement with DDT and, as a result, all claims against us were dismissed. The settlement amount will not have a material impact on our financial results.

On April 19, 2012, we entered into an Election and Amendment Agreement with certain existing stockholders, or the eligible holders, pursuant to which we granted certain eligible holders the right to purchase from us a set number of Class A common stock at the initial public offering price. We refer to these as the private placement purchase rights. The private placement purchase rights must be exercised, if at all, within five business days after the closing of our initial public offering; furthermore, the private placement purchase rights will not apply if our initial public offering price equals or exceeds $31.09 per share.

Pursuant to the Election and Amendment Agreement, we have also agreed that we will issue to the eligible holders additional shares of Class A common stock if our initial public offering price is less than $27.00 per share. In such event, the total number of additional shares will be calculated by taking the amount by which $27.00 exceeds the initial public offering price per share, dividing that excess amount by the initial public offering price per share and, finally, multiplying the result by the number of shares of Series D preferred stock held by the eligible holders.

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SCHEDULE II—CONSOLIDATED VALUATION AND QUALIFYING ACCOUNTS

(In thousands)

	Balance at Beginning of Period		Additions Charged to Expense		Deductions			Balance at End of Period
Allowance for doubtful accounts:
Year Ended December 31, 2009	$	421	$	1,030	$	(485	)	$	966
Year Ended December 31, 2010		966		1,475		(637	)		1,804
Year Ended December 31, 2011		1,804		1,911		(134	)		3,581
Allowance for deferred tax assets:
Year Ended December 31, 2009	$	6,139	$	—	$	(6,139	)		—
Year Ended December 31, 2010		—		1,617		—			1,617
Year Ended December 31, 2011		1,617		10		—			1,627

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PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 13. Other Expenses of Issuance and Distribution

The following table sets forth the fees and expenses, other than underwriting discounts and commissions, payable in connection with the registration of the Class A common stock hereunder. All amounts are estimates except the SEC registration fee, the FINRA filing fee and The NASDAQ Stock Market listing fee.

Securities and Exchange Commission registration fee	$	5,730
FINRA filing fee	$	5,500
The NASDAQ Stock Market listing fee	$	25,000
Accounting fees and expenses		*
Legal fees and expenses		*
Transfer agent fees and expenses		*
Printing and engraving expenses		*
Miscellaneous expenses		*
Total expenses	$	*

* To be provided by amendment.

Item 14. Indemnification of Directors and Officers

Section 102 of the Delaware General Corporation Law permits a corporation in its certificate of incorporation or an amendment to eliminate or limit the personal liability of its directors or its stockholders for monetary damages for a breach of fiduciary duty as a director, except where the director breached his or her duty of loyalty, failed to act in good faith, engaged in intentional misconduct or knowingly violated a law, authorized the payment of a dividend or approved a stock repurchase in violation of law or obtained an improper personal benefit. Our amended and restated certificate of incorporation, that will be in effect upon completion of this offering, provides that no director shall be personally liable to us or our stockholders for monetary damages for any breach of fiduciary duty as a director, notwithstanding any provision of law imposing such liability, except to the extent that Delaware law prohibits the elimination or limitation of liability of directors for breaches of fiduciary duty.

Section 145 of the Delaware General Corporation Law provides that a corporation has the power to indemnify a director, officer, employee or agent of the corporation and certain other persons serving at the request of the corporation in related capacities against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlements actually and reasonably incurred by the person in connection with any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative, other than an action by or in the right of the corporation, to which he or she is a party by reason of such position, if such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the best interests of the corporation and, with respect to any criminal action or proceeding, had no reasonable cause to believe his or her conduct was unlawful, except that, in the case of actions brought by or in the right of the corporation, no indemnification shall be made with respect to any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the Court of Chancery or other adjudicating court determines that, despite the adjudication of liability but in view of all of the circumstances of the case, such person is fairly and reasonably entitled to indemnify for such expenses which the Court of Chancery or such other court shall deem proper. Section 145(g) of the Delaware General Corporation Law further authorizes a corporation to purchase and maintain insurance on behalf of any indemnified person against any liability asserted against and incurred by such person in any indemnified capacity, or arising out of such person’s status as such, regardless of whether the corporation would otherwise have the power to indemnify under Delaware law.

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Our amended and restated certificate of incorporation that will be in effect upon completion of this offering will provide that we must indemnify our directors and officers to the fullest extent authorized by Delaware law and may also pay expenses incurred in defending any such proceeding in advance of its final disposition upon delivery of an undertaking, by or on behalf of an indemnified person, to repay all amounts so advanced if it should be determined ultimately that such person is not entitled to be indemnified under this section or otherwise.

Our amended and restated by-laws that will be in effect upon completion of this offering will provide that it will indemnify each person who was or is a party or threatened to be made a party to any threatened, pending or completed action, suit or proceeding whether civil, criminal, administrative or investigative by reason of the fact that he or she is or was, or has agreed to become, its director or officer, or is or was serving, or has agreed to serve, at its request as a director, officer, partner, employee or trustee of, or in a similar capacity with, another corporation, partnership, joint venture, trust or other enterprise, an “indemnitee,” or by reason of any action alleged to have been taken or omitted in such capacity, against all expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred in connection with such action, suit or proceeding and any appeal therefrom.

We expect our directors and executive officers to execute a new form of indemnification agreement prior to completion of this offering. In general, these agreements provide that we will indemnify the director or executive officer to the fullest extent permitted by law for claims arising in his or her capacity as a director or officer or in connection with his or her service at our request for another corporation or entity. We also maintain a general liability insurance policy that covers certain liabilities of our directors and officers arising out of claims based on acts or omissions in their capacities as directors or officers.

The indemnification rights set forth above shall not be exclusive of any other right which an indemnified person may have or hereafter acquire under any statute, provision of our amended and restated certificate of incorporation, our amended and restated by-laws, agreement, vote of stockholders or disinterested directors or otherwise.

We expect to maintain standard policies of insurance that provide coverage (1) to our directors and officers against loss rising from claims made by reason of breach of duty or other wrongful act and (2) to us with respect to indemnification payments that we may make to such directors and officers.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers or persons controlling the registrant pursuant to the foregoing provisions, the registrant has been informed that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Act and is therefore unenforceable.

Item 15. Recent Sales of Unregistered Securities

Set forth below is information regarding shares of common stock and preferred stock issued and options and warrants granted by us within the past three years that were not registered under the Securities Act. Also included is the consideration, if any, received by us for such securities and information relating to the section of the Securities Act, or rule of the SEC, under which exemption from registration was claimed.

(a) Issuances of Capital Stock

On November 13, 2009, we issued 25,000 restricted shares of our common stock, par value $0.001 per share, to a consultant for services rendered to us, all of which were fully vested on the date of issuance.

On February 11, 2010, we issued an aggregate of 54,986 restricted shares of our common stock, par value $0.001, to 27 of our employees in lieu of a portion of their 2009 cash bonus all of which were fully vested on the date of issuance.

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On May 6, 2010, in connection with the acquisition of swoodoo, we issued an aggregate of 825,000 shares of our common stock, par value $0.001, to the former holders of the outstanding equity of swoodoo, and paid an additional $6,781,000 in cash, net.

On July 30, 2010, we issued to AOL Inc. 962,224 shares of our common stock, pursuant to the exercise of a warrant dated February 25, 2005 to purchase common stock at an exercise price of $1.403 per share, for an aggregate purchase price of $1,350,000.27.

On January 31, 2011, we issued an aggregate of 14,905 restricted shares of our common stock to 14 of our employees in lieu of a portion of their 2010 cash bonus all of which were fully vested on the date of issuance.

(b) Stock Option Grants

During the three year period ended April 11, 2012, we have granted to employees, consultants and directors options to purchase 6,787,590 shares of our common stock under our Third Amended and Restated 2005 Equity Incentive Plan. The exercise price per share ranged from $7.50 to $25.50. Options to purchase shares of our common stock pursuant to our Third Amended and Restated 2005 Equity Incentive Plan generally vest either 25% on the first anniversary of the vesting start date, with the remainder vesting in 36 equal monthly installments, or in 48 equal monthly installments.

During the three year period ended April 11, 2012, an aggregate of 701,363 shares of our common stock were issued upon exercise of outstanding stock options, with exercise prices ranging from $1.00 to $14.82 per share; of that amount, 154,000 shares of our common stock were issued under our 2004 Equity Incentive Plan and 547,363 shares of our common stock were issued under our Third Amended and Restated 2005 Equity Incentive Plan.

During the period between January 1, 2012 and April 11, 2012, we have granted to employees options to purchase 463,000 shares of our common stock under our Third Amended and Restated 2005 Equity Incentive Plan.

During the period between January 1, 2012 and April 11, 2012, an aggregate of 12,500 shares of our common stock were issued upon exercise of outstanding stock options, with an exercise price per share of $14.82. All such shares were issued under our Third Amended and Restated 2005 Equity Incentive Plan.

(c) Concurrent Private Placements

On April 19, 2012, the registrant entered into an Election and Amendment Agreement with certain existing stockholders, pursuant to which up to $             million of Class A common stock may be issued at the initial public offering price, if the initial public offering price is less than $31.09 per share. In addition, if the initial public offering price is less than $27.00 per share, then the registrant will issue a total number of additional shares calculated by taking the amount by which $27.00 exceeds the initial public offering price per share, dividing it by the initial public offering price per share and, finally, multiplying the result by             , which is the number of shares of Series D preferred stock held by the stockholders entitled to the private placement purchase rights.

No underwriters were involved in the foregoing issuances of securities. The offers, sales and issuances of the securities described above were deemed to be exempt from registration under the Securities Act in reliance upon Rule 701 or Regulation S under the Securities Act or Section 4(2) of the Securities Act. The offers, sales and issuances of the securities that were deemed to be exempt in reliance on Rule 701 were transactions under compensatory benefit plans and contracts relating to compensation as provided under Rule 701. The transactions in the securities that were deemed to be exempt in reliance on Regulation S were offers and sales that occurred outside the U.S. as provided under Regulation S. The offers, sales and issuances of the securities that were deemed to be exempt in reliance upon Section 4(2) were each transactions not involving any public offering, and all recipients of these securities were accredited investors within the meaning of Rule 501 of Regulation D of the Securities Act who were acquiring the applicable securities for investment and not distribution and had represented that they could bear the risks of the investment. Each of the recipients of securities in these transactions had adequate access, through employment, business or other relationships, to information about us.

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Item 16. Exhibits and Financial Statement Schedules

(a) Exhibits

Exhibit Index

Exhibit No.		Description
	1.1*	Form of Underwriting Agreement.
	3.1(a)	Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.2(a)	Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.3(a)	Second Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.4(a)	Third Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.5(a)	Fourth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.6(a)	Fifth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.7(f)	Sixth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.8(f)	Seventh Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.9*	Form of Amended and Restated Certificate of Incorporation of the Company, to be in effect upon completion of the offering.
	3.10	Amended and Restated By-Laws of the Company, as currently in effect (originally filed as Exhibit 3.8 with the initial Registration Statement on Form S-1 filed on November 17, 2010 and filed herewith).
	3.11*	Form of Amended and Restated By-Laws of the Company, to be in effect upon completion of the offering.
	3.12	Eighth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	4.1*	Form of Registrant’s Class A Common Stock Certificate.
	4.2	Sixth Amended and Restated Stock Restriction and Co-Sale Agreement, dated December 22, 2011, between the Company and the holders and investors named therein, as amended to date.
	4.3(a)	Sixth Amended and Restated Investor Rights Agreement, dated March 22, 2010, between the Company and the certain investors and founders named therein, as amended to date.
	4.4(a)	First Amendment to the Sixth Amended and Restated Investor Rights Agreement, dated October 1, 2010, between the Company and certain investors and founders named therein.
	4.5(f)	Second Amendment to the Sixth Amended and Restated Investor Rights Agreement, dated February 10, 2012, between the Company and certain investors and founders named therein.
	4.6	Stockholders’ Agreement, dated May 6, 2010, between the Company and the holders and investors named therein, as amended to date (originally filed as Exhibit 4.5 with the initial Registration Statement on Form S-1 filed on November 17, 2010 and filed herewith).
	4.7	First Amendment to the Stockholders’ Agreement, dated December 22, 2011, between the Company and the investors named therein.
	4.8*	Form of Registrant’s Class B Common Stock Certificate.
	4.9	Election and Amendment Agreement, dated April 19, 2012, between the Company and the stockholders named therein.

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Exhibit No.		Description
	5.1*	Form of Opinion of Bingham McCutchen LLP.
	10.1(a)	2004 Stock Incentive Plan.
	10.2(a)	Third Amended and Restated 2005 Equity Incentive Plan, amended by First Amendment, dated January 31, 2008, Second Amendment, dated February 28, 2008, Third Amendment, dated August 27, 2008, Fourth Amendment, dated July 22, 2009, Fifth Amendment, dated December 9, 2009 and Sixth Amendment, dated September 17, 2010.
	10.3*	Form of 2012 Equity Incentive Plan, to be in effect upon completion of the offering.
	10.4(a)^	Services Agreement, dated March 3, 2005, between the Company and ITA Software, Inc.
	10.5(d)^	Amendment to Services Agreement, dated July 18, 2007, between the Company and ITA Software, Inc.
	10.6(a)^	Letter Agreement, dated March 11, 2008, between the Company, SideStep, Inc. and ITA Software, Inc.
	10.7(d)^	Second Amendment to Services Agreement, dated January 1, 2009, between the Company and ITA Software, Inc.
	10.8(a)	Lease Agreement, dated August 7, 2008 between the Company and Jefferson at Maritime, L.P.
	10.9(a)	Office Lease Agreement, dated September 26, 2008, between the Company and Normandy Concord Acquisition, LLC.
	10.10(d)^	Amended and Restated Promotion Agreement, dated April 23, 2009, between the Company and Orbitz Worldwide, LLC.
	10.11(a)	Letter Agreement, dated November 24, 2009 by Jefferson at Maritime L.P. to the Company.
	10.12(a)	Office Lease, dated November 25, 2009, between the Company and SPF Mathilda, LLC.
	10.13(d)^	Google Services Agreement, dated November 1, 2010, between the Company and Google Inc.
	10.14(a)^	KAYAK Insertion Order: IO02703, dated December 16, 2009, between the Company and Expedia.
	10.15(a)^	KAYAK Insertion Order: IO03294, dated April 12, 2010, between the Company and Expedia.
	10.16(a)^	KAYAK Insertion Order: IO03886, dated August 31, 2010, between the Company and Expedia.
	10.17(a)^	KAYAK Insertion Order: IO03850, dated August 19, 2010, between the Company and Expedia UK.
	10.18(a)^	KAYAK Insertion Order: IO03927, dated September 16, 2010, between the Company and Expedia UK.
	10.19(a)^	KAYAK Insertion Order: IO03934, dated September 17, 2010, between the Company and Expedia UK.
	10.20(a)	Standard Terms and Conditions for Internet Advertising for Media Buys One Year or Less v 2.0.
	10.21(a)	Form of Insertion Order under Standard Terms and Conditions for Internet Advertising for Media Buys One Year or Less v 2.0.
	10.22†(b)	Executive Employment Agreement, dated March 2, 2004, between the Company and Daniel Stephen Hafner.
	10.23†(b)	First Amendment to Executive Employment Agreement and Restricted Stock Agreement, dated March 1, 2007, between the Company and Daniel Stephen Hafner.
	10.24†(b)	Second Amendment to Executive Employment Agreement, dated June 26, 2008 between the Company and Daniel Stephen Hafner.
	10.25†(b)	Executive Employment Agreement, dated March 2, 2004, between the Company and Paul M. English.

II-5

Exhibit No.	Description
10.26†(b)	First Amendment to Executive Employment Agreement and Restricted Stock Agreement, dated March 1, 2007, between the Company and Paul M. English.
10.27†(b)	Second Amendment to Executive Employment Agreement, dated June 26, 2008, between the Company and Paul M. English.
10.28†(b)	Offer Letter, dated October 22, 2007, from the Company to Karen Ruzic Klein.
10.29†(b)	Offer Letter, dated April 9, 2009, from the Company to Robert M. Birge.
10.30†(b)	Offer Letter, dated September 30, 2009, from the Company to Melissa H. Reiter.
10.31†(b)	Stock Option Agreement, dated April 29, 2010, between the Company and Daniel Stephen Hafner.
10.32†(b)	Stock Option Agreement, dated April 29, 2010, between the Company and Paul M. English.
10.33†(b)	Stock Option Agreement, dated November 1, 2007, between the Company and Karen Ruzic Klein.
10.34†(b)	Option Amendment Agreement, dated July 7, 2009, between the Company and Karen Ruzic Klein.
10.35†(b)	Stock Option Agreement, dated October 1, 2010, between the Company and Karen Ruzic Klein.
10.36†(b)	Stock Option Agreement, dated May 19, 2009, between the Company and Robert M. Birge.
10.37†(b)	Stock Option Agreement, dated October 1, 2010, between the Company and Robert M. Birge.
10.38†(b)	Stock Option Agreement, dated February 11, 2010, between the Company and Melissa H. Reiter.
10.39†(b)	Stock Option Agreement, dated October 1, 2010, between the Company and Melissa H. Reiter.
10.40†(b)	Stock Option Agreement, dated June 1, 2007, between the Company and Terrell B. Jones.
10.41†(b)	Stock Option Agreement, dated May 19, 2009, between the Company and Terrell B. Jones.
10.42†(b)	Stock Option Agreement, dated March 1, 2004, between the Company and Terrell B. Jones.
10.43†(b)	Stock Option Agreement, dated March 1, 2004, between the Company and Gregory E. Slyngstad.
10.44†(b)	Stock Option Agreement, dated June 1, 2007, between the Company and Gregory E. Slyngstad.
10.45†(b)	Stock Option Agreement, dated May 19, 2009, between the Company and Gregory E. Slyngstad.
10.46†(b)	Restricted Stock Agreement, dated as of March 2, 2004, by and between the Company and Paul M. English.
10.47†(b)	Restricted Stock Grant Agreement, dated as of March 15, 2007, between the Company and Paul M. English.
10.48†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Paul M. English.
10.49†(b)	Restricted Stock Agreement, dated as of March 2, 2004, by and between the Company and Daniel Stephen Hafner.
10.50†(b)	Restricted Stock Grant Agreement, dated as of March 15, 2007, between the Company and Daniel Stephen Hafner.
10.51†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Daniel Stephen Hafner.
10.52†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Karen Ruzic Klein.
10.53†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Robert M. Birge.
10.54†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Terrell B. Jones.
10.55†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Joel E. Cutler.

II-6

Exhibit No.	Description
10.56†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Michael Moritz.
10.57†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Hendrik W. Nelis.
10.58†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Gregory E. Slyngstad.
10.59†*	Form of Indemnification Agreement between the Company and certain of its directors and executive officers, to be in effect upon completion of this offering.
10.60(a)	Commencement Date Agreement, dated March 12, 2009, between the Company and Normandy Concord Acquisition, LLC.
10.61(b)	Amendment No. 1 to Google Services Agreement, dated November 1, 2010, between the Company and Google Inc.
10.62	Intentionally Reserved.
10.63(d)	Offer Letter, dated May 9, 2011, from the Company to Willard H. Smith.
10.64(f)	Seventh Amendment, dated February 10, 2012, to the Third Amended and Restated 2005 Equity Incentive Plan.
10.65(f)	Offer Letter Amendment, dated March 6, 2012, from the Company to Melissa Reiter.
10.66^	Amadeus Products and Services Agreement, effective as of January 1, 2012, between the Company and Amadeus IT Group S.A.
10.67	Election and Amendment Agreement, dated April 19, 2012, between the Company and the stockholders named therein (included in Exhibit 4.9).
14.1*	Code of Business Conduct and Ethics.
21.1(f)	List of Subsidiaries.
23.1*	Form of Consent of Bingham McCutchen LLP (included in Exhibit 5.1).
23.2	Consent of PricewaterhouseCoopers LLP, independent registered public accounting firm.
23.3(f)	Consent of TNS Custom Research, Inc. dated February 21, 2012.
23.4(e)	Consent of TNS Custom Research, Inc. dated October 31, 2011.
24.1(a)	Power of Attorney (included on signature page).
24.2(c)	Power of Attorney.
24.3(f)	Power of Attorney.

* To be filed by amendment.

(a) Previously filed with the initial Registration Statement on Form S-1 filed on November 17, 2010.

(b) Previously filed with Amendment No. 2 to the Registration Statement on Form S-1 filed on January 14, 2011

(c) Previously filed with Amendment No. 4 to the Registration Statement on Form S-1 filed on March 8, 2011.

(d) Previously filed with Amendment No. 5 to the Registration Statement on Form S-1 filed on May 27, 2011.

(e) Previously filed with Amendment No. 8 to the Registration Statement on Form S-1 filed on November 23, 2011.

(f) Previously filed with Amendment No. 9 to the Registration Statement on Form S-1 filed on March 9, 2012.

II-7

† Indicates a management contract or compensatory plan or arrangement.

^ Portions of this exhibit have been omitted pursuant to a confidential treatment request. This information has been filed separately with the Securities and Exchange Commission.

(b) Financial Statement Schedules

Refer to the financial statement schedule provided on page F-30 of the prospectus. All other schedules have been omitted because the information required to be set forth therein is not applicable.

Item 17. Undertakings.

The undersigned Registrant hereby undertakes to provide to the underwriters at the closing specified in the underwriting agreement, certificates in such denomination and registered in such names as required by the underwriter to permit prompt delivery to each purchaser.

Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that, in the opinion of the Securities and Exchange Commission, such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

The undersigned Registrant hereby undertakes that:

(1) For purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in the form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of the registration statement as of the time it was declared effective.

(2) For purposes of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

II-8

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has duly caused this registration statement on Form S-1 to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Norwalk, State of Connecticut on April 20, 2012.

KAYAK SOFTWARE CORPORATION
By:	/s/ Daniel Stephen Hafner
Name:	Daniel Stephen Hafner
Title:	President, Chief Executive Officer and Director

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities held on the dates indicated.

Signature	Title	Date
/s/    Daniel Stephen Hafner         Daniel Stephen Hafner	President and Chief Executive Officer and Director (Principal Executive Officer)	April 20, 2012
/s/    Melissa H. Reiter         Melissa H. Reiter	Chief Financial Officer (Principal Financial Officer and Accounting Officer)	April 20, 2012
/s/    Paul M. English         Paul M. English	Chief Technology Officer and Director	April 20, 2012
* Joel E. Cutler	Director	April 20, 2012
* Terrell B. Jones	Director	April 20, 2012
* Michael Moritz	Director	April 20, 2012
* Hendrik W. Nelis	Director	April 20, 2012
Brian H. Sharples	Director	April 20, 2012
* Gregory S. Stanger	Director	April 20, 2012

*By:	/s/    Daniel Stephen Hafner
	Name:   Daniel Stephen Hafner
	Title:     Attorney-in-fact

Exhibit Index

Exhibit No.		Description
	1.1*	Form of Underwriting Agreement.
	3.1(a)	Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.2(a)	Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.3(a)	Second Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.4(a)	Third Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.5(a)	Fourth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.6(a)	Fifth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.7(f)	Sixth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.8(f)	Seventh Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	3.9*	Form of Amended and Restated Certificate of Incorporation of the Company, to be in effect upon completion of the offering.
	3.10	Amended and Restated By-Laws of the Company, as currently in effect (originally filed as Exhibit 3.8 with the initial Registration Statement on Form S-1 filed on November 17, 2010 and filed herewith).
	3.11*	Form of Amended and Restated By-Laws of the Company, to be in effect upon completion of the offering.
	3.12	Eighth Amendment to Amended and Restated Certificate of Incorporation of the Company, as currently in effect.
	4.1*	Form of Registrant’s Class A Common Stock Certificate.
	4.2	Sixth Amended and Restated Stock Restriction and Co-Sale Agreement, dated December 22, 2011, between the Company and the holders and investors named therein, as amended to date.
	4.3(a)	Sixth Amended and Restated Investor Rights Agreement, dated March 22, 2010, between the Company and the certain investors and founders named therein, as amended to date.
	4.4(a)	First Amendment to the Sixth Amended and Restated Investor Rights Agreement, dated October 1, 2010, between the Company and certain investors and founders named therein.
	4.5(f)	Second Amendment to the Sixth Amended and Restated Investor Rights Agreement, dated February 10, 2012, between the Company and certain investors and founders named therein.
	4.6	Stockholders’ Agreement, dated May 6, 2010, between the Company and the holders and investors named therein, as amended to date (originally filed as Exhibit 4.5 with the initial Registration Statement on Form S-1 filed on November 17, 2010 and filed herewith).
	4.7	First Amendment to the Stockholders’ Agreement, dated December 22, 2011, between the Company and the investors named therein.
	4.8*	Form of Registrant’s Class B Common Stock Certificate.
	4.9	Election and Amendment Agreement, dated April 19, 2012, between the Company and the stockholders named therein.
	5.1*	Form of Opinion of Bingham McCutchen LLP.
	10.1(a)	2004 Stock Incentive Plan.

Exhibit No.	Description
10.2(a)	Third Amended and Restated 2005 Equity Incentive Plan, amended by First Amendment, dated January 31, 2008, Second Amendment, dated February 28, 2008, Third Amendment, dated August 27, 2008, Fourth Amendment, dated July 22, 2009, Fifth Amendment, dated December 9, 2009 and Sixth Amendment, dated September 17, 2010.
10.3*	Form of 2012 Equity Incentive Plan, to be in effect upon completion of the offering.
10.4(a)^	Services Agreement, dated March 3, 2005, between the Company and ITA Software, Inc.
10.5(d)^	Amendment to Services Agreement, dated July 18, 2007, between the Company and ITA Software, Inc.
10.6(a)^	Letter Agreement, dated March 11, 2008, between the Company, SideStep, Inc. and ITA Software, Inc.
10.7(d)^	Second Amendment to Services Agreement, dated January 1, 2009, between the Company and ITA Software, Inc.
10.8(a)	Lease Agreement, dated August 7, 2008 between the Company and Jefferson at Maritime, L.P.
10.9(a)	Office Lease Agreement, dated September 26, 2008, between the Company and Normandy Concord Acquisition, LLC.
10.10(d)^	Amended and Restated Promotion Agreement, dated April 23, 2009, between the Company and Orbitz Worldwide, LLC.
10.11(a)	Letter Agreement, dated November 24, 2009 by Jefferson at Maritime L.P. to the Company.
10.12(a)	Office Lease, dated November 25, 2009, between the Company and SPF Mathilda, LLC.
10.13(d)^	Google Services Agreement, dated November 1, 2010, between the Company and Google Inc.
10.14(a)^	KAYAK Insertion Order: IO02703, dated December 16, 2009, between the Company and Expedia.
10.15(a)^	KAYAK Insertion Order: IO03294, dated April 12, 2010, between the Company and Expedia.
10.16(a)^	KAYAK Insertion Order: IO03886, dated August 31, 2010, between the Company and Expedia.
10.17(a)^	KAYAK Insertion Order: IO03850, dated August 19, 2010, between the Company and Expedia UK.
10.18(a)^	KAYAK Insertion Order: IO03927, dated September 16, 2010, between the Company and Expedia UK.
10.19(a)^	KAYAK Insertion Order: IO03934, dated September 17, 2010, between the Company and Expedia UK.
10.20(a)	Standard Terms and Conditions for Internet Advertising for Media Buys One Year or Less v 2.0.
10.21(a)	Form of Insertion Order under Standard Terms and Conditions for Internet Advertising for Media Buys One Year or Less v 2.0.
10.22†(b)	Executive Employment Agreement, dated March 2, 2004, between the Company and Daniel Stephen Hafner.
10.23†(b)	First Amendment to Executive Employment Agreement and Restricted Stock Agreement, dated March 1, 2007, between the Company and Daniel Stephen Hafner.
10.24†(b)	Second Amendment to Executive Employment Agreement, dated June 26, 2008 between the Company and Daniel Stephen Hafner.
10.25†(b)	Executive Employment Agreement, dated March 2, 2004, between the Company and Paul M. English.
10.26†(b)	First Amendment to Executive Employment Agreement and Restricted Stock Agreement, dated March 1, 2007, between the Company and Paul M. English.
10.27†(b)	Second Amendment to Executive Employment Agreement, dated June 26, 2008, between the Company and Paul M. English.

Exhibit No.	Description
10.28†(b)	Offer Letter, dated October 22, 2007, from the Company to Karen Ruzic Klein.
10.29†(b)	Offer Letter, dated April 9, 2009, from the Company to Robert M. Birge.
10.30†(b)	Offer Letter, dated September 30, 2009, from the Company to Melissa H. Reiter.
10.31†(b)	Stock Option Agreement, dated April 29, 2010, between the Company and Daniel Stephen Hafner.
10.32†(b)	Stock Option Agreement, dated April 29, 2010, between the Company and Paul M. English.
10.33†(b)	Stock Option Agreement, dated November 1, 2007, between the Company and Karen Ruzic Klein.
10.34†(b)	Option Amendment Agreement, dated July 7, 2009, between the Company and Karen Ruzic Klein.
10.35†(b)	Stock Option Agreement, dated October 1, 2010, between the Company and Karen Ruzic Klein.
10.36†(b)	Stock Option Agreement, dated May 19, 2009, between the Company and Robert M. Birge.
10.37†(b)	Stock Option Agreement, dated October 1, 2010, between the Company and Robert M. Birge.
10.38†(b)	Stock Option Agreement, dated February 11, 2010, between the Company and Melissa H. Reiter.
10.39†(b)	Stock Option Agreement, dated October 1, 2010, between the Company and Melissa H. Reiter.
10.40†(b)	Stock Option Agreement, dated June 1, 2007, between the Company and Terrell B. Jones.
10.41†(b)	Stock Option Agreement, dated May 19, 2009, between the Company and Terrell B. Jones.
10.42†(b)	Stock Option Agreement, dated March 1, 2004, between the Company and Terrell B. Jones.
10.43†(b)	Stock Option Agreement, dated March 1, 2004, between the Company and Gregory E. Slyngstad.
10.44†(b)	Stock Option Agreement, dated June 1, 2007, between the Company and Gregory E. Slyngstad.
10.45†(b)	Stock Option Agreement, dated May 19, 2009, between the Company and Gregory E. Slyngstad.
10.46†(b)	Restricted Stock Agreement, dated as of March 2, 2004, by and between the Company and Paul M. English.
10.47†(b)	Restricted Stock Grant Agreement, dated as of March 15, 2007, between the Company and Paul M. English.
10.48†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Paul M. English.
10.49†(b)	Restricted Stock Agreement, dated as of March 2, 2004, by and between the Company and Daniel Stephen Hafner.
10.50†(b)	Restricted Stock Grant Agreement, dated as of March 15, 2007, between the Company and Daniel Stephen Hafner.
10.51†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Daniel Stephen Hafner.
10.52†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Karen Ruzic Klein.
10.53†(b)	Restricted Stock Grant Agreement, dated as of February 11, 2010, between the Company and Robert M. Birge.
10.54†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Terrell B. Jones.
10.55†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Joel E. Cutler.
10.56†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Michael Moritz.
10.57†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Hendrik W. Nelis.
10.58†(b)	Director Indemnification Agreement, dated April 15, 2008, between the Company and Gregory E. Slyngstad.

Exhibit No.	Description
10.59†*	Form of Indemnification Agreement between the Company and certain of its directors and executive officers, to be in effect upon completion of this offering.
10.60(a)	Commencement Date Agreement, dated March 12, 2009, between the Company and Normandy Concord Acquisition, LLC.
10.61(b)	Amendment No. 1 to Google Services Agreement, dated November 1, 2010, between the Company and Google Inc.
10.62	Intentionally Reserved.
10.63(d)	Offer Letter, dated May 9, 2011, from the Company to Willard H. Smith.
10.64(f)	Seventh Amendment, dated February 10, 2012, to the Third Amended and Restated 2005 Equity Incentive Plan.
10.65(f)	Offer Letter Amendment, dated March 6, 2012, from the Company to Melissa Reiter.
10.66^	Amadeus Products and Services Agreement, effective as of January 1, 2012, between the Company and Amadeus IT Group S.A.
10.67	Election and Amendment Agreement, dated April 19, 2012, between the Company and the stockholders named therein (included in Exhibit 4.9).
14.1*	Code of Business Conduct and Ethics.
21.1(f)	List of Subsidiaries.
23.1*	Form of Consent of Bingham McCutchen LLP (included in Exhibit 5.1).
23.2	Consent of PricewaterhouseCoopers LLP, independent registered public accounting firm.
23.3(f)	Consent of TNS Custom Research, Inc. dated February 21, 2012.
23.4(e)	Consent of TNS Custom Research, Inc. dated October 31, 2011.
24.1(a)	Power of Attorney (included on signature page).
24.2(c)	Power of Attorney.
24.3(f)	Power of Attorney.

* To be filed by amendment.

(a) Previously filed with the initial Registration Statement on Form S-1 filed on November 17, 2010.

(b) Previously filed with Amendment No. 2 to the Registration Statement on Form S-1 filed on January 14, 2011.

(c) Previously filed with Amendment No. 4 to the Registration Statement on Form S-1 filed on March 8, 2011.

(d) Previously filed with Amendment No. 5 to the Registration Statement on Form S-1 filed on May 27, 2011.

(e) Previously filed with Amendment No. 8 to the Registration Statement on Form S-1 filed on November 23, 2011.

(f) Previously filed with Amendment No. 9 to the Registration Statement on Form S-1 filed on March 9, 2012.

† Indicates a management contract or compensatory plan or arrangement.

^ Portions of this exhibit have been omitted pursuant to a confidential treatment request. This information has been filed separately with the Securities and Exchange Commission.

EX-3.8

Exhibit 3.10

AMENDED AND RESTATED

BY-LAWS

OF

KAYAK SOFTWARE CORPORATION

ARTICLE I

Offices

Registered Offices; Other Offices. Kayak Software Corporation (the Corporation shall at all times maintain a registered office within the State of Delaware. The Corporation may have such other offices, either within or outside of the State of Delaware, as the business of the Corporation may require from time to time.

ARTICLE II

Stockholders

SECTION 2.1. Annual Meeting. An annual meeting of the stockholders shall be held on the first Tuesday of May of each year, or on such other date as may be determined by resolution of the Board of Directors of the Corporation (the “Board of Directors”); provided, however, that if in any year such date is a legal holiday, such meeting shall be held on the next succeeding business day. At each annual meeting, the stockholders shall elect directors to hold office for the term provided in Section 3.1 of these By-laws.

SECTION 2.2. Special Meeting. A special meeting of the stockholders may be called by the President of the Corporation, the Board of Directors, or by such other officers or persons as the Board of Directors may designate. In addition, unless otherwise required by the laws of the State of Delaware, any Series A Director or Series C Director (as such terms are defined in the Certificate of Incorporation of the Corporation) may call a special meeting of the stockholders.

SECTION 2.3. Place of Stockholders Meetings. The Board of Directors may designate any place, either within or without the State of Delaware, as the place of meeting for any annual meeting or for any special meeting. If no such place is designated by the Board of Directors, the place of meeting will be the principal business office of the Corporation. Notwithstanding the foregoing, the Board of Directors may, in its sole discretion, determine that the meeting shall not be held in any place, but may instead be held solely by means of electronic or telephonic communication, upon such guidelines as the Board of Directors shall determine; provided however that such-guidelines are consistent with Section 211 of the General Corporation Law of the State of Delaware, as the same may be from time to time amended.

SECTION 2.4. Notice of Meetings. (a) Unless waived as herein provided, whenever stockholders are required or permitted to take any action at a meeting, notice of the meeting shall be given in writing or by electronic transmission stating the place if any, date and hour of the meeting, the means of remote communication, if any, by which stockholders and proxy holders may be deemed to be present in person and vote at such meeting, and, in the case of a special meeting, the purpose or purposes for which the meeting is called. Such written or electronic notice shall be given not less than ten (10) days nor more than sixty (60) days before the date of the meeting to each stockholder entitled to vote at the meeting or in the event of a merger, consolidation, share exchange, dissolution or sale, lease or exchange of all or substantially all of the Corporation’s property, business or assets not less than twenty (20) days before the date of the meeting. If mailed, notice is given when deposited in the United States mail, postage prepaid, directed to the stockholder at the stockholder’s address as it appears on the records of the Corporation. If notice is given by facsimile transmission, notice is deemed to be given when directed to a number at which the stockholder has consented to receive notice. If notice is given by electronic mail, notice is deemed to be given when directed to an electronic mail address at which the stockholder has consented to receive notice or if notice is given by posting on an electronic network together with separate notice to the stockholder of such specific posting notice is deemed to be given upon the later of (a) such posting arid (b) the giving of such separate notice. If notice is given by any other means of electronic transmission, notice is deemed to be given when directed to the stockholder.

(b) Notwithstanding the foregoing, notice given to stockholders by e-mail, facsimile or other electronic transmission shall be effective provided that notice is given by a form of e-mail, facsimile or other electronic transmission consented to by the stockholders to whom the notice is given. Any such consent is revocable by the stockholder by written notice to the Corporation. Consent shall be deemed to be given by any stockholder that provides an e-mail, facsimile or other electronic transmission address to the Corporation. Any such consent shall be deemed to be revoked if (i) the Corporation is unable to deliver two consecutive notices by e-mail, facsimile or electronic transmission and (ii) such inability becomes known to the corporate secretary, any assistant secretary or the transfer agent or such other person responsible for giving notice, provided however that the inadvertent failure to treat such inability as a revocation shall not invalidate any meeting or other action.

(c) When a meeting is adjourned to another time or place, if any, in accordance with Section 2.5 of these By-laws, notice need not be given of the adjourned meeting if the time and place, if any, and the means of remote communication, if any, by which stockholders and proxy holders may be deemed to be present in person and voting at such adjourned meeting are announced at the meeting in which the adjournment is taken. At the adjourned meeting, the Corporation may conduct any business which might have been transacted at the original meeting. If the adjournment is for more than thirty (30) days, or if after the adjournment a new record date is fixed for the adjourned meeting, a notice of the adjourned meeting shall be given to each stockholder of record entitled to vote at the meeting.

SECTION 2.5. Quorum and Adjourned Meetings. Unless otherwise provided by law or the Corporation’s Certificate of Incorporation, a majority of the shares entitled to vote, present in person or represented by proxy, shall constitute a quorum at a meeting of stockholders. Unless

otherwise provided by law or the Corporation’s Certificate of Incorporation, if less than a majority of the shares entitled to vote at a meeting of stockholders is present in person or represented by proxy at such meeting, a majority of the shares so represented may adjourn the meeting from time to time without further notice. At any adjourned meeting at which a quorum is present, any business may be transacted which might have been transacted at the original meeting. The stockholders present at a meeting may continue to transact business until adjournment, notwithstanding the withdrawal of such number of stockholders as may leave less than a quorum.

SECTION 2.6. Fixing of Record Date. (a) For the purpose of determining stockholders entitled to notice of or to vote at any meeting of stockholders or any adjournment thereof, the Board of Directors may fix a record date, which record date shall not precede the date upon which the resolution fixing the record date is adopted by the Board of Directors, and which record date shall not be more than sixty (60) nor less than ten (10) days before the date of such meeting. If no record date is fixed by the Board of Directors, the record date for determining stockholders entitled to notice of or to vote at a meeting of stockholders shall be at the close of business on the day next preceding the day on which notice-is given, or, if notice is waived, at the close of business on the day next preceding the day on which the meeting is held. A determination of stockholders of record entitled to notice of or to vote at a meeting of stockholders shall apply to any adjournment of the meeting; provided, however, that the Board of Directors may fix a new record date for the adjourned meeting.

(b) For the purpose of determining stockholders entitled to consent to corporate action in writing without a meeting, the Board of Directors may fix a record date, which record date shall not precede the date upon which the resolution fixing the record date is established by the Board of Directors, and which date shall not be more than ten (10) days after the date on which the resolution fixing the record date is adopted by the Board of Directors. If no record date has been fixed by the Board of Directors, the record date for determining stockholders entitled to consent to corporate action in writing without a meeting, when no prior action by the Board of Directors is required by law, shall be the first date on which a signed written consent setting forth the action taken or proposed to be taken is delivered to the Corporation by delivery to its registered office in the State of Delaware, its principal office, or an officer or agent of the Corporation having custody of the book in which the proceedings of meetings of stockholders are recorded. Delivery to the Corporation’s registered office shall be by hand or by certified or registered mail, return receipt requested. If no record date has been fixed by the Board of Directors and prior action by the Board of Directors is required by law, the record date for determining stockholders entitled to consent to corporate action in writing without a meeting shall be the close of business on the day on which the Board of Directors adopts the resolution taking such prior action.

(c) For the purpose of determining the stockholders entitled to receive payment of any dividend or other distribution or allotment of any rights or the stockholders entitled to exercise any rights in respect to any change, conversion or exchange of stock, or for the purpose of any other lawful action, the Board of Directors may fix the record date, which record date shall not precede the date upon which the resolution fixing the record date is adopted, and which record date shall be not more than sixty (60) days prior to such action. If no record date is fixed,

the record date for determining the stockholders for any such purpose shall be the close of business on the day on which the Board of Directors adopts the resolution relating thereto.

SECTION 2.7.Voting List. The officer who has charge of the stock ledger of the Corporation shall prepare and make, at least ten (10) days before every meeting of stockholders, a complete list of stockholders entitled to vote at the meeting, arranged in alphabetical order, and showing the address of each stockholder and the number of shares registered in the name of each stockholder. Unless otherwise required by law, the Corporation shall not be required to include electronic mail or other electronic contact information in such list of stockholders. Such list shall be open to the examination of any stockholder, for any purpose germane to the meeting, during ordinary business hours, for a period of at least ten (10) days prior to the meeting, (i) on a reasonably accessible electronic network, provided that the information required to gain access to such list is provided with the notice of the meeting, or (ii) during ordinary business hours at the principal place of business of the Corporation. In the event that the Corporation determines to make the list available on an electronic network, the Corporation may take reasonable steps to ensure that such information is available only to stockholders of the Corporation. If the meeting is to be held at a place, then the list shall be produced and kept at the place of the meeting during the whole time thereof, and may be inspected by any stockholder that is present. If the meeting is to be held solely by means of remote communication, then the list shall also be open to the examination of any stockholder during the whole time of the meeting on a reasonably accessible electronic network, and the information required to access such list shall be provided with the notice of the meeting.

SECTION 2.8. Voting. Unless otherwise provided by the Certificate of Incorporation, (i) each stockholder shall be entitled to one vote for each share of capital stock held by each stockholder, (ii) in all, matters other than the election of directors, the affirmative vote of the majority of shares present in person or represented by proxy at the meeting and entitled to vote on the subject matter shall be the act of the stockholders, and (iii) directors shall be elected by plurality of the votes of the shares present in person or represented by a proxy at the meeting entitled to vote on the election of directors.

SECTION 2.9. Proxies. Each stockholder entitled to vote at a meeting of stockholders or to express consent or dissent to corporate action in writing without a meeting may authorize another person or persons to act for him by proxy, but no such proxy shall be voted or acted upon after three years from its date, unless the proxy provides for a longer period. A duly executed proxy shall be irrevocable if it states that it is irrevocable and if, and only as long as, it is coupled with an interest sufficient in law to support an irrevocable power. A proxy may remain irrevocable regardless of whether the interest with which it is coupled is an interest in the stock itself or an interest in the Corporation generally.

SECTION 2.10. Ratification of Acts of Directors and Officers. Except as otherwise provided by law or by the Certificate of Incorporation of the Corporation, any transaction or contract or act of the Corporation or of the directors or the officers of the Corporation may be ratified by the affirmative vote of the holders of the number of shares which would have been necessary to approve such transaction, contract or act at a meeting of stockholders, or by the written consent of stockholders in lieu of a meeting.

SECTION 2.11. Informal Action of Stockholders. (a) Any action required to be taken at any annual or special meeting of stockholders of the Corporation, or any action which may be taken at any annual or special meeting of such stockholders, may be taken without a meeting, without prior notice and without a vote, if a consent or consents in writing, setting forth the action so taken, shall be signed by the holders of outstanding stock having not less than the minimum number of votes that would be necessary to authorize or take such action at a meeting at which all shares entitled to vote thereon were present and voted. Prompt notice of the taking of the corporate action without a meeting by less than unanimous written consent shall be given to those stockholders who have not consented in writing. In the event that the action which is consented to is such as would have required the filing of a certificate with any governmental body, if such action had been voted on by stockholders at a meeting thereof, the certificate filed shall state, in lieu of any statement required by law concerning any vote of stockholders, that written consent has been given in accordance with the provisions of Section 228 of the Delaware General Corporation Law, and that written notice has been given as provided in such section.

(b) A telegram, cablegram, facsimile or other electronic transmission consenting to an action to be taken and transmitted by a stockholder or proxy holder, or by a person or persons authorized to act for a stockholder or proxy holder, shall be deemed to be written, signed and dated for the purposes of this section, provided that any such telegram, cablegram, facsimile, or other electronic transmission sets forth or is delivered with information from which the corporation can determine (i) that the telegram, cablegram, facsimile or other electronic transmission was transmitted by the stockholder or proxy holder or by a person or persons authorized to act for the stockholder or proxy holder and (ii) the date on which such stockholder or proxy holder or authorized person or persons transmitted such telegram, cablegram, facsimile or electronic transmission. The date on which such telegram, cablegram, facsimile or electronic transmission is transmitted shall be deemed to be the date on which such consent was signed. No consent given by telegram, cablegram, facsimile or other electronic transmission shall be deemed to have been delivered until such consent is reproduced in paper form and until such paper form shall be delivered to the corporation by delivery to its registered office, its principal place of business or an officer or agent of the corporation having custody of the book in which proceedings of meetings of stockholders are recorded. Delivery made to a corporation’s registered office shall be made by hand or by certified or registered mail, return receipt requested. Notwithstanding the foregoing limitations on delivery, consents given by telegram, cablegram, facsimile or other electronic transmission may be otherwise delivered to the principal place of business of the corporation or to an officer or agent of the corporation having custody of the book in which proceedings of meetings of stockholders are recorded, if, to the extent and in the manner provided by resolution of the Board of Directors.

(c) Any copy, facsimile or other reliable reproduction of a consent in writing may be substituted or used in lieu of the original writing for any and all purposes for which the original writing could be used, provided that such copy, facsimile or other reproduction shall be a complete reproduction of the entire original writing.

SECTION 2.12. Organization. Such person as the Board of Directors may designate or, in the absence of such a designation, the President of the Corporation or, in his or her absence,

such person as may be chosen by the holders of a majority of the shares entitled to vote who are present, in person or by proxy, shall call to order any meeting of the stockholders and act as chairman of such meeting. In the absence of the Secretary of the Corporation, the chairman of the meeting shall appoint a person to serve as secretary at the meeting.

ARTICLE III

DIRECTORS

SECTION 3.1. Number and Tenure of Directors. The number of directors shall be determined in the manner provided in the Certificate of Incorporation. Each director shall hold office until the next annual meeting of stockholders such and director’s successor is elected and qualified or until such director’s earlier death, resignation or removal. Any director may resign at any time upon written notice to the Corporation. Such notice may be given either in writing or by means of electronic transmission.

SECTION 3.2. Election of Directors. Directors shall be elected at the annual meeting of stockholders, except as provided in Section 3.9 of these By-laws, in the manner provided in the Certificate of Incorporation.

SECTION 3.3. Regular Meetings. Regular meetings of the Board of Directors may be held without notice at such time and in such place as shall from time to time be determined by the Board or the Board may determine that the meeting shall not be held in any place, but by means of remote communication.

SECTION 3.4. Annual Meetings. The first meeting of each newly elected Board of Directors shall be held immediately following the adjournment of the annual meeting of stockholders at the same place as such annual meeting, and no notice of such meeting shall be necessary to the newly elected directors in order to legally constitute the meeting, provided that a quorum shall be present. In the event that such meeting is not held at the time and place, the meeting may be held at such time and place as shall be specified in a notice given as hereinafter provided for special meetings of the Board of Directors, or as shall be specified in a written waiver of notice signed by all of the directors.

SECTION 3.5. Special Meetings. Special meetings of the Board of Directors may be called by or at the request of the Chairman of the Board, a majority of the number of directors constituting the whole board or, unless otherwise required by the laws of the State of Delaware, any Series A Director or Series C Director. The person or persons authorized to call special meetings of the Board of Directors may fix any place, either within or without the State of Delaware, as the place for holding any special meeting of the Board of Directors called by them, or such person or persons may determine that the meeting shall not be held in any place, but by means of remote communication, provided however, that no special meeting of the Board of Directors may be held by means of remote communication if the Board of Directors does not permit regular meetings of the Board of Directors to be held by means of remote communication.

SECTION 3.6. Notice of Special Meetings of the Board of Directors. Notice of any special meeting of the Board of Directors shall be given at least two (2) days prior to the special meeting either in writing or by electronic transmission to each director at his or her address. If mailed, such notice shall be deemed to be delivered when deposited in the United States Mail so addressed, with first-class postage thereon prepaid. If sent by e-mail or other electronic transmission, such notice shall be deemed to be given upon direction to the e-mail or other electronic address of record of the director. If sent by any other means (including facsimile, courier, or express mail, or the like) such notice shall be deemed to be delivered when actually delivered to the home or business address of the director.

SECTION 3.7. Quorum. A majority of the total number of directors fixed by these By-laws, or in the absence of a By-Law which fixes the number of directors, the number stated in the Certificate of Incorporation or named by the incorporators, shall constitute a quorum for the transaction of business. If less than a majority of the directors are present at a meeting of the Board of Directors, a majority of the directors present may adjourn the meeting from time to time without further notice.

SECTION 3.8. Voting. The vote of the majority of the directors present at a meeting at which a quorum is present shall be the act of the Board of Directors, unless the Delaware General Corporation Law or the Certificate of Incorporation requires a vote of a greater number.

SECTION 3.9. Vacancies. Any vacancies or newly created directorships in the Board of Directors shall be filled in the manner provided in the Certificate of Incorporation.

SECTION 3.10. Removal of Directors. Except as required by the laws of the State of Delaware, a director, or the entire Board of Directors, may be removed in the manner provided in the Certificate of Incorporation.

SECTION 3.11. Informal Action of Directors. Unless otherwise restricted by the Certificate of Incorporation or these By-laws, any action required or permitted to be taken at any meeting of the Board of Directors, or of any committee thereof, may be taken without a meeting if all members of the Board of Directors or committee, as the case may be, consent thereto in writing or by electronic transmission, and the writing or writings or electronic transmission or transmissions are filed with the minutes of proceedings of the Board of Directors or committee. Such filings shall be in paper form if the minutes are maintained in paper form and in electronic form if the minutes are maintained in electronic form.

SECTION 3.12. Participation by Conference Telephone. Members of the Board of Directors, or any committee designated by such board, may participate in a meeting of the Board of Directors, or committee thereof, by means of conference telephone or other communications equipment as long as all persons participating in the meeting can speak with and hear each other, and participation by a director pursuant to this Section 3.12 shall constitute presence in person at such meeting.

ARTICLE IV

WAIVER OF NOTICE

SECTION 4.1. Written Waiver of Notice. A written waiver of any required notice, signed by the person entitled to notice, or a waiver by electronic transmission by the person entitled to notice, whether before or after the date stated therein, shall be deemed equivalent to notice. Neither the business to be transacted at, nor the purpose of, any regular or special meeting of stockholders, directors or members of a committee of directors need be specified in any written waiver of notice or any waiver by electronic transmission.

SECTION 4.2. Attendance as Waiver of Notice. Attendance of a person at a meeting shall constitute a waiver of notice of such meeting, except when the person attends a meeting for the express purpose of objecting, and objects at the beginning of the meeting, to the transaction of any business because the meeting is not lawfully called or convened.

ARTICLE V

COMMITTEES

SECTION 5. General Provisions. The Board of Directors may, by resolution passed by a majority of the whole Board, designate one or more committees, each committee to consist of one or more of the directors of the Corporation. The Series A Directors may serve on any committee designated by the Board, including, without limitation, any compensation or audit committee. The Board may designate one or more directors as alternate members of any committee, who may replace any absent or disqualified member at any meeting of the committee. In the absence or disqualification of a member at any meeting of a committee, the member or members thereof present at any meeting and not disqualified from voting, whether or not such member or members constitute a quorum, may unanimously appoint another member of the Board of Directors to act at the meeting in the place of any such absent or disqualified member. Any such committee, to the extent provided in the resolution of the Board of Directors, shall have and may exercise all the powers and authority of the Board of Directors in the management of the business and affairs of the Corporation, and may authorize the seal of the Corporation to be affixed to all papers which may require it; but no such committee shall have the power or authority in reference to amending the Certificate of Incorporation, adopting an agreement of merger or consolidation, recommending to the stockholders the sale, lease, or exchange of all or substantially all of the Corporation’s property and assets, recommending to the stockholders a dissolution of the Corporation or a revocation of a dissolution, or amending the By-laws of the Corporation; and, unless the resolution so provides, no such committee shall have the power or authority to declare a dividend, to authorize the issuance of stock or to adopt a certificate of ownership and merger, pursuant to Section 253 of the Delaware General Corporation Law. Any member of any committee appointed by the Board of Directors or

the entire membership of such committee, may be removed, with or without cause, by the vote of a majority of the Board of Directors.

ARTICLE VI

OFFICERS

SECTION 6.1. General Provisions. The Board of Directors shall elect a President, a Secretary and a Treasurer of the Corporation. The Board of Directors may also elect a Chairman of the Board, one or more Vice Presidents, one or more Assistant Secretaries and Assistant Treasurers and such additional officers as the Board of Directors may deem necessary or appropriate from time to time. Any two or more offices may be held by the same person. The officers elected by the Board of Directors shall have such duties as are hereafter described and such additional duties as the Board of Directors may from time to time prescribe.

SECTION 6.2. Election and Term of Office. The officers of the Corporation shall be elected annually by the Board of Directors at the regular meeting of the Board of Directors held after each annual meeting of the stockholders. If the election of officers is not held at such meeting, such election shall be held as soon thereafter as may be convenient. New offices of the Corporation may be created and filled and vacancies in offices may be filled at any time, at a meeting or by the written consent of the Board of Directors. Unless removed pursuant to Section 6.3 of these By-laws, each officer shall hold office until his successor has been duly elected and qualified, or until his earlier death or resignation. Election or appointment of an officer or agent shall not of itself create contract rights.

SECTION 6.3. Removal of Officers. Any officer or agent elected or appointed by the Board of Directors may be removed by the Board of Directors whenever, in its judgment, the best interests of the Corporation would be served thereby, but such removal shall be without prejudice to the contract rights, if any, of the person(s) so removed.

SECTION 6.4. The Chief Executive Officer. The Chief Executive Officer, if one is chosen, shall be the principal executive officer of the Corporation and shall in general supervise and control all of the business and affairs of the Corporation, unless otherwise provided by the Board of Directors. If the Board of Directors has not elected a Chairman from among its members, the Chief Executive Officer shall preside at all meetings of the stockholders and of the Board of Directors. The Chief Executive Officer shall see that orders and resolutions of the Board of Directors are carried into effect. The Chief Executive Officer may sign bonds, mortgages, certificates for shares and all other contracts and documents whether or not under the seal of the Corporation except in cases where the signing and execution thereof shall be expressly delegated by law, by the Board of Directors or by these By-laws to some other officer or agent of the Corporation. The Chief Executive Officer shall have general powers of supervision and shall be the final arbiter of all differences between officers of the Corporation and his decision as to any matter affecting the Corporation shall be final and binding as between the officers of the Corporation subject only to the Board of Directors.

SECTION 6.5. The President. The President shall be the chief operating officer of the Corporation and as such shall have the active management of the business of the Corporation under the general supervision of the Chief Executive Officer. The President shall have concurrent power with the Chief Executive Officer to sign bonds, mortgages, certificates for shares and other contracts and documents, whether or not under the seal of the Corporation except in cases where the signing and execution thereof shall be expressly delegated by law, by the Board of Directors, or by these By-laws to some other officer or agent of the Corporation. In general, the President shall perform all duties incident to the office of president and such other duties as the Chief Executive Officer or the Board of Directors may from time to time prescribe.

SECTION 6.6. The Chairman of the Board. The Chairman of the Board, if one is chosen, shall be chosen from among the members of the board. The Chairman of the Board shall perform such duties as may be assigned to the Chairman of the Board by the Chief Executive Officer or by the Board of Directors.

SECTION 6.7. The Vice President. In the absence of the President or in the event of his inability or refusal to act, the Vice President (or in the event there be more than one Vice President, the Executive Vice President and then the other Vice President or Vice Presidents in the order designated, or in the absence of any designation, then in the order of their election) shall perform the duties of the President, and when so acting, shall have all the powers of and be subject to all the restrictions upon the President. The Vice Presidents shall perform such other duties and have such other powers as the Chief Executive Officer or the Board of Directors may from time to time prescribe.

SECTION 6.8. The Secretary. The Secretary shall attend all meetings of the Board of Directors and all meetings of the stockholders and record all the proceedings of the meetings of the Corporation and of the Board of Directors in a book to be kept for that purpose and shall perform like duties for the standing committees when required. The Secretary shall give, or cause to be given, notice of all meetings of the stockholders and special meetings of the Board of Directors, and shall perform such other duties as may be prescribed by the Board of Directors or the Chief Executive Officer, under whose supervision he shall be. The Secretary shall have custody of the corporate seal of the Corporation and the Secretary, or an Assistant Secretary, shall have authority to affix the same to any instrument requiring it and when so affixed, it may be attested by his signature or by the signature of such Assistant Secretary. The Board of Directors may give general authority to any other officer to affix the seal of the Corporation and to attest the affixing by his signature.

SECTION 6.9. The Assistant Secretary. The Assistant Secretary, or if there be more than one, the Assistant Secretaries in the order determined by the Board of Directors (or if there be no such determination, then in the order of their election), shall, in the absence of the Secretary or in the event of his inability or refusal to act, perform the duties and exercise the powers of the Secretary and shall perform such other duties and have such other powers as the Chief Executive Officer or the Board of Directors may from time to time prescribe.

SECTION 6.10. The Treasurer. The Treasurer shall have the custody of the corporate

funds and securities and shall keep full and accurate accounts of receipts and disbursements in books belonging to the Corporation and shall deposit all moneys and other valuable effects in the name and to the credit of the Corporation in such depositories as may be designated by the Board of Directors. The Treasurer shall disburse the funds of the Corporation as may be ordered by the Board of Directors, taking proper vouchers for such disbursements, and shall render to the President and the Board of Directors, at its regular meetings, or when the Board of Directors so requires, an account of all his transactions as Treasurer and of the financial condition of the Corporation. If required by the Board of Directors, the Treasurer shall give the Corporation a bond (which shall be renewed every six (6) years) in such sum and with such surety or sureties as shall be satisfactory to the Board of Directors for the faithful performance of the duties of his office and for the restoration to the Corporation, in case of his death, resignation, retirement or removal from office, of all books, papers, vouchers, money and other property of whatever kind in his possession or under his control belonging to the Corporation.

SECTION 6.11. The Assistant Treasurer. The Assistant Treasurer, or if there shall be more than one, the Assistant Treasurers in the order determined by the Board of Directors (or if there be no such determination, then in the order of their election), shall, in the absence of the Treasurer or in the event of his inability or refusal to act, perform the duties and exercise the powers of the Treasurer and shall perform such other duties and have such other powers as the Chief Executive Officer or the Board of Directors may from time to time prescribe.

SECTION 6.12. Duties of Officers May be Delegated. In the absence of any officer of the Corporation, or for any other reason the Board of Directors may deem sufficient, the Board of Directors may delegate the powers or duties, or any of such powers or duties, of any officers or officer to any other officer or to any director.

SECTION 6.13. Compensation. The Board of Directors shall have the authority to establish reasonable compensation of all officers for services to the Corporation.

ARTICLE VII

CERTIFICATES FOR SHARES

SECTION 7.1. Certificates of Shares. The shares of the Corporation shall be represented by certificates, provided that the Board of Directors of the Corporation may provide by resolution or resolutions that some or all of any or all classes or series of its stock shall be uncertificated shares. Any such resolution shall not apply to shares represented by a certificate until such certificate is surrendered to the Corporation. Notwithstanding the adoption of such a resolution by the Board of Directors, every holder of stock represented by certificates and upon request every holder of uncertificated shares shall be entitled to have a certificate signed by, or in the name of the Corporation by the Chairman of the Board of Directors, the Chief Executive Officer, the President or any Vice President, and by the Treasurer or an Assistant Treasurer, or the Secretary or an Assistant Secretary of the Corporation representing the number of shares registered in certificate form. Any or all the signatures on the certificate may be a facsimile.

SECTION 7.2. Signatures of Former Officer, Transfer Agent or Registrar. In case any officer, transfer agent, or registrar who has signed or whose facsimile signature has been placed upon a certificate shall have ceased to be such officer, transfer agent or registrar before such certificate is issued, it may be issued by the Corporation with the same effect as if such person or entity were such officer, transfer agent or registrar at the date of issue.

SECTION 7.3. Transfer of Shares. Transfers of shares of the Corporation shall be made only on the books of the Corporation by the holder of record thereof or by his legal representative, who shall furnish proper evidence of authority to transfer, or by his or her attorney thereunto authorized by power of attorney duly executed and filed with the Secretary of the Corporation, and on surrender for cancellation of certificate for such shares. Prior to due presentment of a certificate for shares for registration of transfer, the Corporation may treat a registered owner of such shares as the person exclusively entitled to vote, to receive notifications and otherwise have and exercise all of the right and powers of an owner of shares.

SECTION 7.4. Lost, Destroyed or Stolen Certificates. Whenever a certificate representing shares of the Corporation has been lost, destroyed or stolen, the holder thereof may file in the office of the Corporation an affidavit setting forth, to the best of his knowledge and belief, the time, place, and circumstance of such loss, destruction or theft together with a statement of indemnity sufficient in the opinion of the Board of Directors to indemnify the Corporation against any claim that may be made against it on account of the alleged loss of any such certificate. Thereupon the Board may cause to be issued to such person or such person’s legal representative a new certificate or a duplicate of the certificate alleged to have been lost, destroyed or stolen. In the exercise of its discretion, the Board of Directors may waive the indemnification requirements provided herein.

ARTICLE VIII

DIVIDENDS

SECTION 8. Dividends. The Board of Directors of the Corporation may declare and pay dividends upon the shares of the Corporation’s capital stock in any form determined by the Board of Directors, in the manner and upon the terms and conditions provided by law.

ARTICLE IX

CONTRACTS, LOANS, CHECKS AND DEPOSITS

SECTION 9.1. Contracts. The Board of Directors may authorize any officer or officers, agent or agents, to enter into any contract or execute and deliver any instrument in the name of and on behalf of the Corporation, and such authority may be general or confined to specific instances.

SECTION 9.2. Loans. No loans shall be contracted on behalf of the Corporation and no evidences of indebtedness shall be issued in its name unless authorized by a resolution of the Board of Directors. Such authority may be general or confined to specific instances.

SECTION 9.3. Checks, Drafts, Etc. All checks, drafts or other orders for the payment of money, notes or other evidences of indebtedness issued in the name of the Corporation shall be signed by one or more officers or agents of the Corporation and in such manner as shall from time to time be determined by resolution of the Board of Directors.

SECTION 9.4. Deposits. The funds of the Corporation may be deposited or invested in such bank account, in such investments or with such other depositaries as determined by the Board of Directors.

ARTICLE X

AMENDMENTS

SECTION 11. Amendments. These By-laws may be amended or repealed by the Board of Directors or by the stockholders of the Corporation.

EX-3.12

Exhibit 3.12

EIGHTH AMENDMENT TO

AMENDED AND RESTATED

CERTIFICATE OF INCORPORATION

OF

KAYAK SOFTWARE CORPORATION

(Pursuant to Sections 242 of the

General Corporation Law of the State of Delaware)

KAYAK Software Corporation, a corporation organized and existing under and by virtue of the provisions of the General Corporation Law of the State of Delaware (the “Corporation”),

DOES HEREBY CERTIFY:

1) That the name of this corporation is KAYAK Software Corporation, and that this corporation was originally incorporated pursuant to the General Corporation Law of the State of Delaware (the “DGCL”) on January 14, 2004 under the name Travel Search Company, Inc.;

2) That the Board of Directors duly adopted resolutions proposing to amend the Amended and Restated Certificate of Incorporation of this corporation, declaring said amendment to be advisable and in the best interests of this corporation and its stockholders, and authorizing the appropriate officers of this corporation to solicit the consent of the stockholders therefor;

3) That the Board of Directors of the Corporation directed that such amendment be submitted to the stockholders of the Corporation for their consent and approval and, in lieu of a meeting and vote of stockholders, the stockholders have given written consent to said amendment in accordance with the provisions of Section 228 of the DGCL.

4) That said amendment was duly adopted in accordance with the provisions of Sections 242 and 228 of the DGCL; which resolutions and consent setting forth the proposed amendment and restatement is as follows:

RESOLVED, that the Amended and Restated Certificate of Incorporation of this Corporation, as amended, be further amended to delete the word “and” appearing immediately before clause (ix) in subparagraph B.5E of Article FOURTH and to insert the following new clause (x) in such subparagraph B.5E of Article FOURTH:

“; and (x) shares of Common Stock issued, or deemed issued, pursuant to (A) a firm commitment underwritten public offering consummated pursuant to a Registration Statement under the Securities Act of 1933, as amended, with an effective time on or prior to December 31, 2012 and/or (B) pursuant to the terms of that certain Election and Amendment Agreement, dated on or about April 19, 2012, by and between the Corporation and the other parties thereto”.

[The remainder of this page is intentionally left blank. Signature page follows.]

IN WITNESS WHEREOF this Eighth Amendment to Amended and Restated Certificate of Incorporation has been executed by the undersigned this 19^th day of April, 2012.

KAYAK SOFTWARE CORPORATION
	/s/ Daniel Stephen Hafner
	Name: Daniel Stephen Hafner
	Title: Chief Executive Officer

EX-4.2

Exhibit 4.2

SIXTH AMENDED AND RESTATED

STOCK RESTRICTION AND CO-SALE AGREEMENT

SIXTH AMENDED AND RESTATED STOCK RESTRICTION AND CO-SALE AGREEMENT made this 22^nd day of December, 2011 by and among (i) KAYAK Software Corporation, a Delaware corporation (the “Company”), (ii) holders of Common Stock, or options or warrants to acquire Common Stock whose names are set forth under the heading “Holders” on Schedule I hereto and each person who shall, after the date hereof, acquire shares of Common Stock (or options or warrants to acquire Common Stock) and join in and become a party to this Agreement by executing and delivering to the Company an Instrument of Accession in the form of Schedule II hereto (the persons described in this clause (ii) being referred to collectively as the “Holders” and singularly as a “Holder”) and (iii) those persons whose names are set forth under the heading “Investors” on Schedule I hereto (the persons described in this clause (iii) being referred to collectively as the “Investors”). The Holders and Investors are collectively referred to herein as the “Stockholders”.

WITNESSETH:

WHEREAS, the Holders currently own shares of the Company’s Common Stock, par value $.001 per share (the “Common Stock”) and the Purchaser Warrants (as defined below); and

WHEREAS, certain of the Investors have heretofore purchased from the Company an aggregate of (i) six million six hundred thousand (6,600,000) shares of the Company’s Series A Convertible Preferred Stock, par value $.001 per share (the “Series A Stock”), (ii) one million one hundred seventy six thousand fifty one (1,176,051) shares of the Company’s Series A-1 Convertible Preferred Stock, par value $.001 per share (the “Series A-1 Stock”, and collectively with the Series A Stock, the “Series A Preferred Stock”), (iii) four million nine hundred eighty nine thousand three hundred eight (4,989,308) shares of the Company’s Series B Convertible Preferred Stock, par value $.001 per share (the “Series B Stock”), (iv) two million one hundred thirty eight thousand two hundred seventy five (2,138,275) shares of the Company’s Series B-1 Convertible Preferred Stock, par value $.001 per share (the “Series B-1 Stock”, and collectively with the Series B Stock, the “Series B Preferred Stock”), (v) three million eight hundred fifty five thousand one hundred eighty (3,855,180) shares of the Company’s Series C Convertible Preferred Stock, par value $.001 per share (the “Series C Stock”) and (vi) eight million eight thousand eight hundred forty two (8,008,842) shares of the Company’s Series D Convertible Preferred Stock, par value $.001 per share (the “Series D Stock”, and collectively with the Series A Preferred Stock, the Series B Preferred Stock and the Series C Stock, the “Convertible Preferred Stock”);

WHEREAS, certain of the Investors previously entered into that certain Fifth Amended and Restated Stock Restriction and Co-Sale Agreement, dated as of December 20, 2007 (together with all exhibits thereto, the “Prior Agreement”), in connection with a certain Series D Convertible Stock Purchase Agreement dated as of December 20, 2007 (the “Purchase Agreement”), by and among certain of the Investors and the Company pursuant to which the Company issued the Series D Stock to such Investors; and

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WHEREAS, the Company and the Requisite Investors have mutually agreed to amend and restate the Prior Agreement in its entirety.

NOW, THEREFORE, for good and valuable consideration, the receipt and legal sufficiency of which is hereby acknowledged, the Company, the Holders and the Investors hereby agree to amend and restate the Prior Agreement in its entirety as follows:

1. Prohibited Transfers. The Holders shall not sell, assign, transfer, pledge, hypothecate, mortgage or dispose of, by gift or otherwise, or in any way encumber, all or any part of the Shares (as hereinafter defined) owned by them except in compliance with the terms of this Agreement. For purposes of this Agreement, the term “Shares” shall mean and include all shares of Common Stock (excluding shares of Common Stock issued upon conversion of the Convertible Preferred Stock) and the Warrants to purchase shares of Common Stock issued or issuable pursuant to the terms of the Interactive Marketing Agreement between the Company and America Online, Inc. dated as of November 10, 2004 (the “Purchaser Warrants”). The Company shall not transfer on its books any Shares which are subject to this Agreement unless the provisions hereof have been complied with in full. Any purported transfer by a Holder of Shares without full compliance with the provisions of this Agreement shall be null and void.

2. Right of First Refusal on Dispositions by the Holders. If at any time any Holder wishes to sell, assign, transfer or otherwise dispose of any or all Shares owned by such Holder pursuant to the terms of a bona fide offer received from a third party, such Holder shall submit a written offer to sell such Shares to the Company and the Investors on terms and conditions, including price, not less favorable to the Company and the Investors than those on which such Holder proposes to sell such Shares to such third party (the “Offer”). The Offer shall disclose the identity of the proposed purchaser or transferee, the Shares proposed to be sold or transferred (the “Offered Shares”), the agreed terms of the sale or transfer, including price, and any other material facts relating to the sale or transfer. The Investors shall, subject to the first sentence of Section 3, have the right to purchase, on the same terms and conditions set forth in the Offer, that portion of the Offered Shares to be determined in the manner set forth herein. Each Investor shall have the right to purchase up to that number of Offered Shares as shall be equal to the aggregate Offered Shares multiplied by a fraction, the numerator of which is the number of shares of Common Stock issued or issuable to such Investor upon the conversion of all shares of Convertible Preferred Stock held by such Investor together with the number of shares of Common Stock actually issued upon the exercise of Purchaser Warrants and held by such Investor (the “Conversion Shares”) and the denominator of which is the aggregate number of Conversion Shares held by all Investors. The number of Offered Shares each Investor or Qualified Transferee, as that term is defined below, is entitled to purchase under this Section 2 shall be referred to as such Investor’s “Pro Rata Fraction.” Each Investor shall have the right to transfer its right to any Pro Rata Fraction or part thereof to any Qualified Transferee (as defined below). In the event an Investor does not wish to purchase or to transfer its right to purchase its Pro Rata Fraction, then any Investors who so elect shall have the right to purchase, on a pro rata basis with any other Investors who so elect, any Pro Rata Fraction not purchased by an Investor or Qualified Transferee. Each Investor shall act upon the Offer as soon as practicable after receipt of the Offer, and in all events within fifteen (15) days after receipt of the Offer. Each Investor shall have the right to accept the Offer as to all or part of the Offered Shares. In the event that an Investor shall elect to purchase all or part of the Offered Shares covered by the

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Offer, said Investor shall individually communicate in writing such election to purchase to whichever of the Holders has made the Offer, which communication shall be delivered in accordance with Section 8 below and shall, when taken in conjunction with the Offer be deemed to constitute a valid, legally binding and enforceable agreement for the sale and purchase of the Offered Shares covered thereby.

If the Investors do not exercise their right to purchase all of the Offered Shares from a Holder within said fifteen-day period, such Holder shall promptly notify the Company in writing (the “Company Notice”) as to the number of Offered Shares which the Investors shall not have agreed to purchase (the “Remaining Shares”). Subject to the approval of the holders of at least fifty eight percent (58%) of the votes attributable to all outstanding shares of Convertible Preferred Stock (voting as a separate class on an as-converted to Common Stock basis) (the “Requisite Investors”), the Company shall have the right to purchase all of the Remaining Shares on the same terms and conditions as set forth in the Offer. If the Company elects to purchase any Remaining Shares, it shall notify the Holder within fifteen days after receipt of the Company Notice (the “Final Date”).

For purposes of this Section 2, a “Qualified Transferee” of an Investor shall mean any person (i) who is an Investor, (ii) who is an “affiliated person” of an Investor, as that term is defined in the Investment Company Act of 1940, (iii) who is a partner of an Investor, or (iv) who previously acquired at least 250,000 shares of Convertible Preferred Stock (as adjusted for stock splits, stock dividends, reclassifications, recapitalizations or other similar events).

3. Right of Participation in Sales by Holders. In the event that the Investors and the Company do not exercise their rights under Section 2 with respect to all of the Offered Shares, the transferring Holder may, subject to the provisions of this Section 3, sell, assign, transfer or otherwise dispose of all of the Offered Shares to the third party named in the Offer (the “Purchaser”). Before any such sale, assignment, transfer or other disposition, each Investor shall have the right to require, as a condition to such sale or disposition, that the Purchaser purchase from said Investor at the same price per Share (which shall be calculated on a Common Stock equivalent basis if the Stock (as defined in Section 5) to be sold by an Investor is of a different class or series of stock from that of the Shares) and on the same terms and conditions as involved in such sale or disposition by the Holder up to a number of shares of Stock as is equal to the product of (x) the number of Shares proposed to be sold by the Holder, times (y) a fraction, the numerator of which is the number of Conversion Shares held by such Investor and the denominator of which is the aggregate number of Conversion Shares held by all Investors electing to participate in the sale pursuant to this Section 3 plus the number of shares of Stock owned by the selling Holder (calculated on an as-converted to Common Stock basis). Each Investor wishing so to participate in any such sale or disposition shall notify the selling Holder of such intention as soon as practicable after receipt of the Offer made pursuant to Section 2, and in all events within fifteen (15) days after receipt of the Investor Notice. In the event that an Investor shall elect to participate in such sale or disposition, said Investor shall individually communicate such election to the selling Holder, which communication shall be delivered in accordance with Section 8 below. The Holder and/or each participating Investor shall sell to the Purchaser all, or at the option of the Purchaser, any part of the Stock proposed to be sold by them at not less than the price and upon other terms and conditions, if any, not more favorable to the

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Purchaser than those originally offered; provided, however, that any purchase of less than all of such Stock by the Purchaser shall be made from the Holder and/or each participating Investor pro rata based on the number of shares such Holder and/or Investors would otherwise be entitled to sell to such Purchaser pursuant to this Section 3. The selling Holder or Investor shall use his or its reasonable best efforts to obtain the agreement of the Purchaser to the participation of the participating Investors in the contemplated sale, and shall not sell any Stock to such Purchaser if such Purchaser declines to permit the participating Investors to participate pursuant to the terms of this Section 3. The provisions of this Section 3 shall not apply to the sale of any Shares by a Holder to an Investor pursuant to an Offer under Section 2.

4. Permitted Transfers.

(i) Anything herein to the contrary notwithstanding, the provisions of Sections 1, 2 and 3 shall not apply to: (a) any transfer of Shares by a Holder by gift or bequest or through inheritance to, or for the benefit of, any member or members of his or her immediate family (which shall include any spouse, children or grandchildren) or to a trust, partnership or limited liability company for the benefit of such Holder or such members of his or her immediate family; (b) any transfer of Shares by a Holder to a trust in respect of which he or she serves as trustee, provided that the trust instrument governing said trust shall provide that such Holder, as trustee, shall retain sole and exclusive control over the voting and disposition of said Shares until the termination of this Agreement; (c) any sale of Common Stock in a public offering pursuant to a registration statement filed by the Company with the Securities and Exchange Commission; (d) any repurchase of shares of Common Stock by the Company from officers, employees, directors or consultants of the Company which are subject to restrictive stock purchase agreements under which the Company has the option to repurchase such shares at cost (or a lesser amount) upon the occurrence of certain events; and (e) any repurchase of Shares by the Company pursuant to the Restricted Stock Agreement, dated as of March 2, 2004, by and between the Company and Daniel Stephen Hafner, and the Restricted Stock Agreement, dated as of March 2, 2004, by and between the Company and Paul English (collectively, the “Founder Stock Agreements”).

(ii) In the event of any such transfer, other than pursuant to subsections (i)(c), (d) and (e) of this Section 4, the transferee of the Shares shall hold the Shares so acquired with all the rights conferred by, and subject to all the restrictions imposed by, this Agreement, and as a condition to such transfer, each such transferee shall execute and deliver an Instrument of Accession in the form of Schedule II agreeing to be bound by the provisions of this Agreement.

5. Election of Directors.

(a) Board Designation Rights; Initial Members. Each Stockholder hereby agrees to vote all of the Stock of the Company now owned or hereafter acquired by such party (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions (including, but not limited, to the nomination of specified persons, the execution of written consents and the calling of a stockholder meeting for the purpose of electing such specified persons) to cause and maintain the election to the Board of Directors of the Company, to the extent permitted pursuant to the Company’s Amended and Restated Certificate of Incorporation, as amended from time to time (the “Certificate of Incorporation”), the following:

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(i) the then current Chief Executive Officer of the Company as one (1) of the Common Directors (as defined in the Certificate of Incorporation), who shall initially be Daniel Stephen Hafner;

(ii) one (1) person designated by the holders of a majority of the outstanding shares of Common Stock, voting as a separate class, as the other Common Director, who shall initially be Paul English;

(iii) two (2) persons designated by the holders of at least seventy percent (70%) of the outstanding shares of the Series A Preferred Stock, voting as a separate class on an as-converted to Common Stock basis (the “Series A Designators”), as the two Series A Directors (as defined in the Certificate of Incorporation), who shall initially be Joel Cutler and Terrell Jones;

(iv) one (1) person designated by the holders of at least a majority of the outstanding shares of the Series C Stock, voting as a separate class (the “Series C Designators”), as the Series C Director (as defined in the Certificate of Incorporation), who shall initially be Hendrik Nelis;

(v) for so long as Sequoia Capital Growth Fund III or one or more of its affiliates (as defined in Rule 501 of Regulation D under the Securities Act of 1933, as amended) (“Sequoia”) holds at least 1,000,000 shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar event affecting the Preferred Stock), one (1) person designated by Sequoia as the Series D Director (as defined in the Certificate of Incorporation), who shall initially be Michael Moritz. In the event Sequoia does not hold at least 1,000,000 shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar event affecting the Preferred Stock), then, in lieu of Sequoia, the holders of at least a majority of the outstanding shares of the Series D Stock, voting as a separate class, shall be entitled to designate one (1) person as the Series D Director. The individual, entity, or group of individuals and/or entities who has the right to designate the Series D Director pursuant this Section 5(a)(v) shall be referred to herein as the “Series D Designator”;

(vi) one (1) person designated jointly by the Series A Designators, the Series C Designators and the Series D Designator, each voting as a separate series, as the Preferred and Common Director (as defined in the Certificate of Incorporation), who shall initially be Gregory Stanger; and

(v) one (1) person designated jointly by the Series A Designators, the Series C Designators, and the Series D Designator, each voting as a separate series, as the Remaining Director (as defined in the Certificate of Incorporation), who shall initially be Brian Sharples.

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For the purposes of this Agreement, (x) “Stock” shall mean and include all Convertible Preferred Stock and all shares of Common Stock, and all other securities of the Company which may be exchangeable for, convertible into or issued in exchange for or in respect of shares of Common Stock (whether by way of stock split, stock dividends, combination, reclassification, reorganization or any other means), (y) “Board Designee” shall mean any individual who is designated for election to the Company’s Board of Directors pursuant to this Section 5; and (z) “Designator” or “Designators” shall mean, as applicable, any individual, entity, or group of individuals and/or entities who has the right to designate one (1) or more Board Designees for election to the Company’s Board of Directors pursuant to this Section 5.

(b) Removal; Successor Directors. In the absence of any designation from the appropriate Designator or Designators, the Board Designee previously designated by them and then serving shall be reelected if still eligible to serve as provided herein. From time to time during the term of this Agreement, a Designator or Designators may, in their sole discretion:

(i) elect to initiate the removal from the Company’s Board of Directors of any incumbent Board Designee who occupies a board seat for which such Designator or Designators are entitled to designate the Board Designee under Section 5(a), and/or

(ii) designate a new Board Designee for election to a board seat for which such Designator or Designators are entitled to designate the Board Designee under Section 5(a) (whether to replace a prior Board Designee or to fill a vacancy in such board seat); provided, however, that any new Board Designee designated by the Series A Designators, the Series C Designators and the Series D Designator for the Preferred and Common Director must be ratified by the holders of a majority of the outstanding shares of Common Stock, which ratification may not be unreasonably withheld or delayed; provided further, however, no such ratification is required for any new Board Designee who has general experience with marketing and the travel related e-commerce industry.

In the event of an initiation of removal of a Board Designee pursuant to Section 5(b)(i), the Stockholders shall vote all of the Stock of the Company now owned or hereafter acquired by them (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions to cause the removal from the Company’s Board of Directors of the Board Designee or Designees so designated for removal by the appropriate Designator or Designators; provided, however, in no event shall any party vote to remove any Board Designee unless the appropriate Designator or Designators have so directed pursuant to Section 5(b)(i). In the event of designation of a Board Designee pursuant to Section 5(b)(ii), the parties shall vote all of the Stock of the Company now owned or hereafter acquired by them (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions to cause the election to the Company’s Board of Directors of any new Board Designee or Designees so designated for election to the Company’s Board of Directors pursuant to Section 5(b)(ii).

Without the consent of the Requisite Investors, the parties hereby agree that they will not take any action, by vote or otherwise, to increase the authorized number of directors constituting the Company’s Board of Directors to more than eight (8) directors, unless the holders of

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Convertible Preferred Stock are then entitled to elect, in addition to the two (2) Series A Directors described in Section 5(a)(iii) above and one Series C Director described in Section 5(a)(iv) above, two additional Series A Directors and one additional Series C Director pursuant to Article 4B, subparagraph 6C of the Certificate of Incorporation (the “Additional Directors”), in which case the Company’s Board of Directors shall consist of no more than eleven (11) members. If and for so long as the holders of Convertible Preferred Stock are entitled to elect the Additional Directors pursuant to Article 4B, subparagraph 6C of the Certificate of Incorporation, each of the parties hereto hereby agrees to vote all of the Stock of the Company now owned or hereafter acquired in favor of the election to the Board of Directors of two (2) persons designated from time to time by the Series A Designators and one (1) person designated from time to time by the Series C Designators.

(c) Observer Rights. Oak Investment Partners XII, Limited Partnership shall be entitled to have a representative (the “Oak Board Observer”) attend all meetings of the Company’s Board of Directors and all committees thereof in a nonvoting capacity (subject to the Company’s determination upon the advice of counsel that the Oak Board Observer’s presence may violate attorney-client privilege or would otherwise be excused from a meeting were the Oak Board Observer a director) and, in this respect, the Company shall give the Oak Board Observer copies of all notices, minutes, consents and other materials that it provides to its directors. The Oak Board Observer may participate in discussions of matters brought to the Company’s Board of Directors. As a condition to attending such meetings and receiving such materials, the Oak Board Observer will agree in writing to hold in confidence and trust and not use or disclose any confidential information provided to or learned by it in connection with its rights under this paragraph as if the Oak Board Observer were a member of the Company’s Board of Directors.

6. Drag-Along Rights. If (a) a majority of the members of the Company’s Board of Directors and (b) the Requisite Investors approve a sale of Company or all or substantially all of Company’s assets, whether by means of a merger, consolidation, sale of stock or assets or otherwise (a “Sale of the Company”), all Investors and Holders shall consent to and vote their Shares in favor of the Sale of the Company, and if the Sale of the Company is structured as (i) a merger or consolidation of the Company, or a sale of all or substantially all of the Company’s assets, each Investor and Holder shall waive any dissenters’ rights, appraisal rights or similar rights in connection with such merger, consolidation or asset sale, or (ii) a sale of the stock of the Company, the Investors and Holders shall agree to sell their Shares on the terms and conditions approved by (x) a majority of the members of the Company’s Board of Directors and (y) the Requisite Investors; provided, however, that, (A) all proceeds from such Sale of the Company shall be payable to the holders of the Company’s Stock in accordance with the Certificate of Incorporation, including, without limitation, Article 4B, Paragraph 3 thereof, which entitles the holders of Convertible Preferred Stock to a liquidation preference payment and other rights set forth therein, except that, at the discretion of the Company’s Board of Directors, holders of shares of Common Stock that are unvested on the date that the Sale of the Company is consummated may receive, in lieu of proceeds from the Sale of the Company and in exchange for their unvested shares of Common Stock, unvested securities or options to acquire securities of the entity surviving the Sale of the Company on an equitable basis, (B) except as set forth in the preceding clause (A), the terms of such Sale of the Company applicable to holders of shares

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of each series of Convertible Preferred Stock, in their capacities as holders thereof, shall be no less favorable than the terms applicable to the holders of all other series of Convertible Preferred Stock in their capacities as holders thereof and (C) if the Requisite Investors are given the option to choose the form of consideration to be received in such Sale of the Company on its Stock, the obligations of a Holder or other Investor to approve the Sale of the Company under this Section 6 shall be conditioned upon it having received the same option. Each Holder and Investor hereby irrevocably constitutes and appoints the Company and any representative or agent thereof, with full power of substitution, as its true and lawful attorney-in-fact with full irrevocable power and authority in the place and stead of such Holder or Investor and in the name of such Holder or Investor or in its own name, for the purpose of carrying out the terms of this Section 6, to take any and all appropriate action and to execute any and all documents and instruments which may be necessary or desirable to accomplish the purposes of this Section 6. Such Holder and Investor hereby ratifies all that said attorneys shall lawfully do or cause to be done by virtue hereof.

7. Termination. This Agreement, and the respective rights and obligations of the parties hereto, shall terminate upon the completion of a firm commitment underwritten public offering of Common Stock in which (a) the aggregate gross proceeds received by the Company shall be at least $25,000,000, and (b) the per share price paid by the public for such shares shall be at least $31.09 (appropriately adjusted to reflect any subdivision or combination of the Common Stock occurring after the date hereof) (a “Qualified Public Offering”); provided, however, that Sections 1 through 3 shall terminate on the earlier of (i) the completion of a Qualified Public Offering and (ii) ten (10) years after the date hereof.

8. Notices. Any notices or other communication required to be sent or given hereunder by any of the parties shall in every case be in writing and shall be deemed properly served if (a) delivered personally, (b) sent by certified U.S. Mail, with first class postage prepaid, return receipt requested, (c) delivered by a recognized overnight courier service, with certification of receipt requested, or (d) sent by facsimile transmission with a confirmation copy sent by overnight courier, in each case, to the parties at the addresses and telecopy numbers as set forth below or at such other addresses or telecopy number as may be furnished in writing by any party pursuant to this Section 8 (except that notices of changes of address or a telecopy number shall only be effective upon receipt):

if to the Company or any other party hereto that is also a party to the Purchase Agreement, at the address of such party set forth in the Purchase Agreement, with a copy sent to such party’s legal counsel designated in the Purchase Agreement, if applicable;

if to any other party hereto as of the date of the Agreement, to such party at its address set forth on Schedule I hereto;

if to a Holder who subsequently becomes a party to this Agreement, at its address set forth on the Instrument of Accession pursuant to which such Holder became a party to this Agreement; and

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if to an Investor who subsequently becomes a party to this Agreement, at its address set forth on the Instrument of Accession pursuant to which such Investor became a party to this Agreement.

Date of service of such notice shall be (w) the date such notice is personally delivered, (x) three (3) days after the date of mailing if sent by certified mail, (y) two (2) days after date of delivery to the overnight courier if sent by overnight courier (as evidenced by a written receipt from the courier), or (z) the next succeeding business day after transmission by facsimile.

9. Failure to Deliver Shares. If a Holder becomes obligated to sell any Shares owned by, or held for the benefit of, such Holder to an Investor or a Qualified Transferee under this Agreement and fails to deliver such Shares in accordance with the terms of this Agreement, such Investor may, at its option, in addition to all other remedies it may have, send to the Company for the benefit of such Holder the purchase price for such Shares as is herein specified. Thereupon, the Company upon written notice to said Holder, (a) shall cancel on its books the certificate(s) representing the Shares to be sold and (b) shall issue, in lieu thereof, in the name of such Investor, a new certificate(s) representing such Shares, and thereupon all of said Holder’s rights in and to such shares shall terminate. The Company may exercise a similar remedy in enforcing its rights under Section 2. If a Holder transfers any Shares to a Purchaser in violation of this Agreement, the Company may, at the election of a majority of the disinterested members of the Company’s Board of Directors, cancel on the books of the Company any shares of capital stock then held by such Holder, and any such breaching Holder agrees to purchase from the Purchasers and any transferee a number of shares of capital stock equal to the amount so transferred in violation of this Agreement.

10. Specific Performance; Proxy. The rights of the parties under this Agreement are unique and, accordingly, the parties shall, in addition to such other remedies as may be available to any of them at law or in equity, have the right to enforce their rights hereunder by actions for specific performance to the extent permitted by law. The voting of shares of capital stock pursuant to this Agreement may be effected in person, by proxy, by written consent or in any other manner permitted by applicable law. Each Stockholder hereby grants to the Secretary of the Company, in the event that such Stockholder fails to vote its shares of capital stock as required by this Agreement, a proxy coupled with an interest in all shares of capital stock owned by such Stockholder empowering the Secretary to vote such shares as to such matters as are set forth in Section 5 hereof, which proxy is irrevocable until this Agreement terminates pursuant to its terms or this Section 10 is amended to remove such grant of proxy in accordance with Section 14 of this Agreement.

11. Legend. The certificates representing the Shares shall bear on their face a legend indicating the existence of the restrictions imposed hereby.

12. Entire Agreement. This Agreement, the Founder Stock Agreements and the Purchase Agreement (including any and all exhibits, schedules and other instruments contemplated thereby) constitute the entire agreement among the parties with respect to the subject matter hereof and supersede all prior agreements or understandings between them or any of them as to such subject matter.

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13. Waivers and Further Agreements. Except as provided in Section 14, any of the provisions of this Agreement may be waived by an instrument in writing executed and delivered by Requisite Investors. Any waiver by any party of a breach of any provision of this Agreement shall not operate or be construed as a waiver of any subsequent breach of that provision or of any other provision hereof. Each of the parties hereto agrees to execute all such further instruments and documents and to take all such further action as any other party may reasonably require in order to effectuate the terms and purposes of this Agreement. Notwithstanding the foregoing, no waiver may treat one Investor more adversely than any other Investor without the consent of such Investor adversely affected by such waiver.

14 Amendments. Except as otherwise expressly provided herein, this Agreement may not be amended except by an instrument in writing executed by (i) the Company and (ii) the Requisite Investors. Notwithstanding the foregoing, (i) the consent of the Holders holding a majority of the outstanding shares of Common Stock subject to this Agreement shall be required for any amendment that materially adversely affects the rights of the Holders, (ii) no amendment may treat one Investor more adversely than any other Investor without the consent of such Investor adversely affected by such amendment, (iii) no amendment may treat one Holder more adversely than any other Holder without the consent of such Holder, and (iv) no amendment, waiver or modification to the rights of a Designator to appoint or remove a Board Designee pursuant to Section 5 shall be effective without the consent of such Designator.

15. Assignment; Successors and Assigns. This Agreement shall be binding upon and shall inure to the benefit of the parties hereto and their respective heirs, executors, legal representatives, successors and permitted transferees, except as may be expressly provided otherwise herein.

16. Severability. In case any one or more of the provisions contained in this Agreement shall for any reason be held to be invalid, illegal or unenforceable in any respect, such invalidity, illegality or unenforceability shall not affect any other provision of this Agreement and such invalid, illegal and unenforceable provision shall be reformed and construed so that it will be valid, legal, and enforceable to the maximum extent permitted by law.

17. Counterparts. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

18. Section Headings. The headings contained in this Agreement are for reference purposes only and shall not in any way affect the meaning or interpretation of this Agreement.

19. Governing Law. This Agreement shall be construed and enforced in accordance with and governed by the laws of the General Corporation Law of the State of Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to its principles of conflicts of laws.

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20. Additional Parties. Any purchaser of Convertible Preferred Stock shall become a party to this Agreement by executing and delivering to the Company an executed Instrument of Accession in the form of Schedule II hereto. Upon such execution and delivery, such purchaser shall be deemed to be an “Investor” hereunder with all of the rights and obligations thereof. Unless otherwise consented to by the Board of Directors, the Company shall cause each officer, director, employee, consultant or other service provider of the Company who acquires shares of Common Stock representing greater than 1% of the fully-diluted capital stock of the Company or options to purchase such number of shares of Common Stock, to become a party to this agreement by executing and delivering to the Company an executed Instrument of Accession in the form of Schedule II hereto. Upon such execution and delivery, such holder shall be deemed to be a “Holder” hereunder with all of the rights and obligations thereof.

[signature pages follow]

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IN WITNESS WHEREOF, the undersigned have executed this Sixth Amended and Restated Stock Restriction and Co-Sale Agreement as a sealed instrument as of the day and year first above written.

COMPANY:

KAYAK SOFTWARE CORPORATION
By:	/s/ Steve Hafner
Name:	Steve Hafner
Title:	CEO

[The remainder of this page is intentionally left blank.]

Signature Page to Sixth A&R Co-Sale Agreement

HOLDERS:

/s/ Daniel Stephen Hafner

Daniel Stephen Hafner

/s/ Paul English

Paul English

McKane 2007 Grandchildren Trust
By:	/s/ Daniel Stephen Hafner
Name:
Title:

J.M. Hafner Trust
By:	/s/ Daniel Stephen Hafner
Name:
Title:

Joseph A. Hafner Trust
By:	/s/ Daniel Stephen Hafner
Name:
Title:

Merrill T. Hafner Trust
By:	/s/ Daniel Stephen Hafner
Name:
Title:

D.S. Hafner Trust
By:	/s/ Daniel Stephen Hafner
Name:
Title:

Signature Page to Sixth A&R Co-Sale Agreement

Hafner Investment Partnership
By:	/s/ Daniel Stephen Hafner
Name:
Title:

The Paul M. English 2007 Irrevocable Family Trust
By:	/s/ Paul M. English
Name:	Paul M. English, Trustee

By:
Name:	Jean A. English, Trustee

The Paul M. English 2006 Irrevocable Family Trust
By:	/s/ Paul M. English
Name:	Paul M. English, Trustee

By:
Name:	Jean A. English, Trustee

Andrew Patterson

Alexander Morcos

Benjamin P. Davenport

John E. Crandon III

Jean A. English

Signature Page to Sixth A&R Co-Sale Agreement

Anastasios Makris

Melissa Fredette

Jonathan Spewak

The Paul M. English 2009 Charitable Remainder Unitrust I

By:	/s/ Paul M. English
Name: Paul M. English, Trustee

By:

Name: Jean A. English, Trustee

The Paul M. English 2009 Charitable Remainder Unitrust II

By:	/s/ Paul M. English
Name: Paul M. English, Trustee

By:

Name: Jean A. English, Trustee

John Bullock

Shehzad Daredia

Signature Page to Sixth A&R Co-Sale Agreement

INVESTORS:

GENERAL CATALYST GROUP II, L.P.		GENERAL CATALYST GROUP III, L.P.
By: General Catalyst Partners II, L.P. Its General Partner		By: General Catalyst Partners III, L.P. Its General Partner
By: General Catalyst GP II, LLC Its General Partner		By: General Catalyst GP III, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald		Name: William J. Fitzgerald
Title: Member and Chief Financial Officer		Title: Member and Chief Financial Officer
GC ENTREPRENEURS FUND II, L.P.		GC ENTREPRENEURS FUND III, L.P.
By: General Catalyst Partners II, L.P. Its General Partner		By: General Catalyst Partners III, L.P. Its General Partner
By: General Catalyst GP II, LLC Its General Partner		By: General Catalyst GP III, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald		Name: William J. Fitzgerald
Title: Member and Chief Financial Officer		Title: Member and Chief Financial Officer
GENERAL CATALYST GROUP V, L.P.		GC ENTREPRENEURS FUND V, L.P.
By: General Catalyst Partners V, L.P. Its General Partner		By: General Catalyst Partners V, L.P. Its General Partner
By: General Catalyst GP V, LLC Its General Partner		By: General Catalyst GP V, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald		Name: William J. Fitzgerald
Title: Member and Chief Financial Officer		Title: Member and Chief Financial Officer

Signature Page to Sixth A&R Co-Sale Agreement

GENERAL CATALYST GROUP V SUPPLEMENTAL, L.P.
By:	General Catalyst Partners V, L.P.
Its General Partner
By:	General Catalyst GP V, LLC
Its General Partner
By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald
Title: Member and Chief Financial Officer

Signature Page to Sixth A&R Co-Sale Agreement

/s/ Daniel Stephen Hafner

Daniel Stephen Hafner

Signature Page to Sixth A&R Co-Sale Agreement

/s/ Paul English

Paul English

Signature Page to Sixth A&R Co-Sale Agreement

ACCEL LONDON II L.P.
By:	Accel London II Associates L.P.
Its:	General Partner
By:	Accel London II Associates L.L.C.
Its:	General Partner
By:	/s/ Jonathan Biggs
	Name:	Jonathan Biggs
	Title:	Attorney in Fact

ACCEL LONDON INVESTORS 2006 L.P.
By:	Accel London II Associates L.L.C.
Its:	General Partner
By:	/s/ Jonathan Biggs
	Name:	Jonathan Biggs
	Title:	Attorney in Fact

Signature Page to Sixth A&R Co-Sale Agreement

SEQUOIA CAPITAL XI

SEQUOIA TECHNOLOGY PARTNERS XI

SEQUOIA CAPITAL XI PRINCIPALS

FUND

By: SC XI Management, LLC

A Delaware Limited Liability Company

General Partner of Each

By:	/s/ Michael Moritz
Name:
Title:	Managing Member

SEQUOIA CAPITAL GROWTH FUND III SEQUOIA CAPITAL GROWTH PARTNERS III SEQUOIA CAPITAL GROWTH III PRINCIPALS FUND
By:	SCGF III Management, LLC A Delaware Limited Liability Company General Partner of Each

By:	/s/ Michael Moritz
Name:
Title:	Managing Member

Signature Page to Sixth A&R Co-Sale Agreement

SCHEDULE I

KAYAK SOFTWARE CORPORATION

SCHEDULE OF HOLDERS AND INVESTORS

Investors:

General Catalyst Group II, L.P.

GC Entrepreneurs Fund II, L.P.

General Catalyst Group III, L.P.

GC Entrepreneurs Fund III, L.P.

General Catalyst Group V, L.P.

General Catalyst Group V Supplemental, L.P.

GC Entrepreneurs Fund V, L.P.

20 University Road, Suite 450

Cambridge, MA 02138

Fax: (617) 234-7040

Attn: Joel Cutler

Daniel Stephen Hafner

33 North Water Street, Apartment 610,

South Norwalk, CT 06854

Fax: (203) 899-3125

Paul English

204 Pleasant Street

Arlington, MA 02476

Greg Slyngstad

1736 W. Beaver Lake Drive SE

Sammamish, WA 98075

Sequoia Capital Growth Fund III

Sequoia Capital Growth Partners III

Sequoia Capital Growth III Principals Fund

Sequoia Capital XI

Sequoia Technology Partners XI

Sequoia Capital XI Principals Fund

3000 Sand Hill Road

Bldg 4, Suite 250

Menlo Park, CA 94025

Accel London II, L.P.

Accel London Investors 2006 L.P.

428 University Avenue

Palo Alto, CA 94301-1812

Fax: (650) 614-4880

Attn: Richard Zamboldi

Notices also sent to

16 St. James’s Street

London SW1A 1ER

United Kingdom

Fax: +44 (0) 20 7170 1099

Attn: Jonathan Biggs

Attn: Harry Nelis

Norwest Venture Partners VII-A LP

Norwest Venture Partners X, LP

525 University Avenue, Suite 800

Palo Alto, CA 94301

650.321.8000

Oak Investment Partners XII, Limited Partnership

One Gorham Island

Westport, CT 06880

Tenaya Capital V, L.P.

Tenaya Capital V V-P, L.P.

Tenaya Capital B, LP

2965 Woodside Road, Suite A

Woodside, CA 94062

Trident Capital Fund-V, L.P

Trident Capital Fund-V Affiliates Fund, L.P.

Trident Capital Fund-V Affiliates Fund (Q), L.P.

Trident Capital Fund-V Principals Fund, L.P.

Trident Capital Parallel Fund-V, C.V.

505 Hamilton Ave, Suite 200

Palo Alto, CA 94301

Gold Hill Venture Lending 03, L.P.

Two Newton Executive Park, Suite 203

Newton, MA 02462

The English Family 2010 Trust

51 Winchester Road

Arlington, MA 02474

Holders:

Daniel Stephen Hafner

33 North Water Street, Apartment 610,

South Norwalk, CT 06854

Fax: (203) 899-3125

Paul English

204 Pleasant Street

Arlington, MA 02476

McKane 2007 Grandchildren Trust

48 Owenoke Park

Westport, CT 06880

J.M. Hafner Trust

6 Longfellow Lane

Houston, TX 77005

Joseph A. Hafner Trust

1316 Pequot Avenue

Southport, CT 06890

Merrill T. Hafner Trust

1316 Pequot Avenue

Southport, CT 06890

Paul M. English and Jean A English, as trustees of The Paul M. English 2007 Irrevocable Family Trust

204 Pleasant Street

Arlington, MA 02476

Paul M. English and Jean A English, as trustees of The Paul M. English 2006 Irrevocable Family Trust

204 Pleasant Street

Arlington, MA 02476

D.S. Hafner Trust

1316 Pequot Avenue

Southport, CT 06890

Hafner Investment Partnership

23 Farnham Park Drive

Houston, TX 77024

Andrew Patterson

50 Murray Street, #1116

New York, NY 10007

Alexander Morcos

310 E 9^th Street, #1

New York, NY 10001

Benjamin P. Davenport

229 Chrystie Street, #813

New York, NY 10002

John E. Crandon III

36 Grattan Street

San Francisco, CA 94117

Anastasios P. Makris

24 18th Street

Lowell, MA 01850

Jean A. English

51 Winchester Road

Arlington, MA 02474

The Paul M. English 2009 Charitable Remainder Unitrust I

204 Pleasant Street

Arlington, MA 02476

The Paul M. English 2009 Charitable Remainder Unitrust II

204 Pleasant Street

Arlington, MA 02476

Jonathan Spewak

1085 Commonwealth Ave. #300

Boston, MA 02215

Melissa Fredette

224 Stevens Street

Marlboro, MA 01752

John Bullock

1 Fawn Circle

Bedford, MA 01730

Shehzad Daredia

295 Park Avenue South

Apt. 160

New York, NY 10010

Kellie Macdonald

5 Green Lane

Unit B

Greenwich, CT 06831

Stephen Squadrito

31 Carp Road

Milford, MA 01757

Nilesh Thakker

18892 Woodleigh Court

Saratoga, CA 95070

Windspeed Ventures III, LP

52 Waltham Street

Lexington, MA 02421

Evergreen Opportunity Fund LLC

1117 Sawgrass Corporate Parkway

Sunrise, FL 33323

Keith D. Melnick

77 Mill Hill Road

Southport, CT 06890

Institutional Venture Partners XII, L.P.

3000 Sand Hill Road

Building 2, Suite 250

Menlo Park, CA 94025

Sprout Opportunity Fund I, LLC

1117 Sawgrass Corporate Parkway

Sunrise, FL 33323

Sprout Opportunity Fund III, LLC

1117 Sawgrass Corporate Parkway

Sunrise, FL 33323

John Bullock & Laura Bullock JT TEN

1 Fawn Circle

Bedford, MA 01730

Leah Rounds

108 Hickory Woods Lane

Stratford, CT 06614

James Giza

15 Pierce Road

Sutton, MA 01590

Robert M. Birge

46 Lyons Plain Road

Weston, CT 06883

Rose O’Donnell

8 Sassafras Road

Westford, MA 01886

Mark S. Dionne

199 Jackson Street

Newton, MA 02459

SCHEDULE II

KAYAK SOFTWARE CORPORATION

INSTRUMENT OF ACCESSION

The undersigned,                                , as a condition precedent to becoming the owner or holder of record of                                     (             ) shares of the                      stock, par value $.001 per share, of KAYAK Software Corporation, a Delaware corporation (the “Company”), or options to purchase such stock, hereby agrees to become a [Holder/Investor] under that certain Fifth Amended and Restated Stock Restriction and Co-Sale Agreement dated as of December         , 2007 by and among the Company and other stockholders of the Company party thereto. This Instrument of Accession shall take effect and shall become an integral part of, and the undersigned shall become a party to and bound by, said Fifth Amended and Restated Stock Restriction and Co-Sale Agreement immediately upon execution and delivery to the Company of this Instrument of Accession.

IN WITNESS WHEREOF, this INSTRUMENT OF ACCESSION has been duly executed by or on behalf of the undersigned, as of the date below written.

Signature:

(Print Name)

Address:

Date:

Accepted:

KAYAK SOFTWARE CORPORATION
By:
	Name:
	Title:

Date:

EX-4.6

Exhibit 4.6

STOCKHOLDERS’ AGREEMENT

STOCKHOLDERS’ AGREEMENT (the “Agreement”) made this 6th day of May, 2010 by and among (i) Kayak Software Corporation, a Delaware corporation (the “Company”), (ii) the holders of the Company’s Common Stock, par value $0.001 per share (the “Common Stock”), whose names are set forth under the heading “Holders” on Schedule I hereto and each person who shall, after the date hereof, acquire shares of Common Stock from such Holders in accordance with the terms of this Agreement and join in and become a party to this Agreement by executing and delivering to the Company an Instrument of Accession in the form set forth on Schedule 11 hereto (the persons described in this clause (ii) being referred to collectively as the “Holders” and singularly as a “Holder”) and (iii) those persons whose names are set forth under the heading “Investors” on Schedule I hereto as the same may be modified from time to time pursuant to Section 18 (the persons described in this clause (iii) being referred to collectively as the “Investors”). Capitalized terms used but not defined in this Agreement shall have the meanings ascribed thereto in the Stock Purchase Agreement, dated as of the date hereof, by and among the Company, the Holders and the Seller Representative (as defined therein) (the “Purchase Agreement’).

WITNESSETH:

WHEREAS, the Company has agreed to issue to the Holders an aggregate of up to Eight Hundred Twenty Five Thousand (825,000) shares of Common Stock pursuant to the Purchase Agreement;

WHEREAS, the execution and delivery of the Agreement by the Company and the Holders is a condition precedent to the obligations of Company and the Holders, respectively, under the Purchase Agreement; and

WHEREAS, each Investor currently holds shares of the Company’s (i) Series A Convertible Preferred Stock, par value $0.001 per share (the “Series A Stock”), (ii) Series A-1 Convertible Preferred Stock, par value $0.001 per share (the “Series A-1 Stock”, and collectively with the Series A Stock, the “Series A Preferred Stock”), (iii) Series B Convertible Preferred Stock, par value $0.001 per share (the “Series B Stock”), (iv) Series B-I Convertible Preferred Stock, par value $0.001 per share (the “Series   B-1 Stock”, and collectively with the Series B Stock, the “Series B Preferred Stock”), (v) Series C Convertible Preferred Stock, par value $0.001 per share (the “Series C Preferred Stock”) and/or (vi) Series D Convertible Preferred Stock, par value $0.001 per share (the “Series D Stock,” and collectively with the Series A Preferred Stock, the Series B Preferred Stock, the Series C Preferred Stock and any other shares of Preferred Stock of the Company issued after the date hereof, the “Convertible Preferred Stock”);

NOW, THEREFORE, for good and valuable consideration, the receipt and legal sufficiency of which is hereby acknowledged, the Company and the Holders hereby agree as follows:

1. Prohibited Transfers. The Holders shall not sell, assign, transfer, pledge, hypothecate, mortgage or dispose of, by gift or otherwise, or in any way encumber, all or any

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part of the Shares (as hereinafter defined) owned by them except in compliance with the terms of this Agreement. For purposes of this Agreement, the term “Shares” shall mean only those shares of Common Stock acquired by the Holders pursuant to the Purchase Agreement. The Company shall not transfer on its books any Shares which are subject to this Agreement unless the provisions hereof have been complied with in full. Any purported transfer by a Holder of Shares without full compliance with the provisions of this Agreement shall be null and void.

2. Right of First Refusal on Dispositions by the Holders. If at any time any Holder wishes to sell, assign, transfer or otherwise dispose of any or all Shares owned by such Holder to a third party, such Holder shall submit a written offer to sell such Shares to the Company and the Investors on terms and conditions, including price, not less favorable to the Company and the Investors than those on which such Holder proposes to sell such Shares to such third party (the “Offer”). The Offer shall disclose the identity of the proposed purchaser or transferee, the Shares proposed to be sold or transferred (the “Offered Shares”), the agreed terms of the sale or transfer, including price, and any other material facts relating to the sale or transfer. The Investors shall, subject to the first sentence of Section 3, have the right to purchase, on the same terms and conditions set forth in the Offer, that portion of the Offered Shares to be determined in the manner set forth herein. Each Investor shall have the right to purchase up to that number of Offered Shares as shall be equal to the aggregate Offered Shares multiplied by a fraction, the numerator of which is the number of shares of Common Stock issued or issuable to such Investor upon the conversion of all shares of Convertible Preferred Stock held by such Investor (the “Conversion Shares”) and the denominator of which is the aggregate number of Conversion Shares held by all Investors. The number of Offered Shares each Investor or Qualified Transferee, as that term is defined below, is entitled to purchase under this Section 2 shall be referred to as such Investor’s “Pro Rata Fraction.” Each Investor shall have the right to transfer its right to any Pro Rata Fraction or part thereof to any Qualified Transferee (as defined below). In the event an Investor does not wish to purchase or to transfer its right to purchase its Pro Rata Fraction, then any Investors who so elect shall have the right to purchase, on a pro rata basis with any other Investors who so elect, any Pro Rata Fraction not purchased by an Investor or Qualified Transferee. Each Investor shall act upon the Offer as soon as practicable after receipt of the Offer, and in all events within fifteen (15) days after receipt of the Offer. Each Investor shall have the right to accept the Offer as to all or part of the Offered Shares. In the event that an Investor shall elect to purchase all or part of the Offered Shares covered by the Offer, said Investor shall individually communicate in writing such election to purchase to whichever of the Holders has made the Offer, which communication shall be delivered in accordance with Section 11 below and shall, when taken in conjunction with the Offer be deemed to constitute a valid, legally binding and enforceable agreement for the sale and purchase of the Offered Shares covered thereby.

If the Investors do not exercise their right to purchase all of the Offered Shares from a Holder within said fifteen-day period, such Holder shall promptly notify the Company in writing (the “Company Notice”) as to the number of Offered Shares which the Investors shall not have agreed to purchase (the “Remaining Shares”). Subject to the approval of the holders of at least fifty eight percent (58%) of the votes attributable to all outstanding shares of Convertible Preferred Stock (voting as a separate class on an as-converted to Common Stock basis) (the “Requisite Investors”), the Company shall have the right to purchase any or all of the Remaining Shares on the same terms and conditions as set forth in the Offer. If the Company elects to purchase any Remaining Shares, it shall notify the Holder within fifteen days after receipt of the Company Notice (the “Final Date”).

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For purposes of this Section 2, a “Qualified Transferee” of an Investor shall mean any person (i) who is an Investor, (ii) who is an “affiliated person” of an Investor, as that term is defined in the Investment Company Act of 1940, (iii) who is a partner of an Investor, or (iv) who previously acquired at least 250,000 shares of Convertible Preferred Stock (as adjusted for stock splits, stock dividends, reclassifications, recapitalizations or other similar events).

3. Right of Participation in Sales by Holders. In the event that the Investors and the Company do not exercise their rights under Section 2 with respect to all of the Offered Shares, then the transferring Holder may, subject to the provisions of this Section 3, sell, assign, transfer or otherwise dispose of the Offered Shares as to which neither the investors nor the Company exercised such rights (such shares, the “Final Remaining Shares”) to the third party named in the Offer (the “Purchaser”). Before any such sale, assignment, transfer or other disposition, each Investor shall have the right to require, as a condition to such sale or disposition, that the Purchaser purchase from said Investor at the same price per Share (which shall be calculated on a Common Stock equivalent basis if the Stock (as defined in Section 6) to be sold by an Investor is of a different class or series of stock from that of the Shares) and on the same terms and conditions as involved in such sale or disposition by the Holder up to a number of shares of Stock as is equal to the product of (x) the number of Final Remaining Shares proposed to be sold by the Holder, times (y) a fraction, the numerator of which is the number of Conversion Shares held by such Investor and the denominator of which is the aggregate number of Conversion Shares held by all investors electing to participate in the sale pursuant to this Section 3 plus the number of shares of Stock owned by the selling Holder (calculated on an as-converted to Common Stock basis). Each Investor wishing so to participate in any such sale or disposition shall notify the selling Holder of such intention as soon as practicable after receipt of the Offer made pursuant to Section 2, and in all events within fifteen (15) days after receipt of the Investor Notice. In the event that an Investor shall elect to participate in such sale or disposition, said Investor shall individually communicate such election to the selling Holder, which communication shall be delivered in accordance with Section 11 below. The Holder and/or each participating Investor shall sell to the Purchaser all, or at the option of the Purchaser, any part of the Stock proposed to be sold by them at not less than the price and upon other terms and conditions, if any, not more favorable to the Purchaser than those originally offered; provided, however, that any purchase of less than all of such Stock by the Purchaser shall be made from the Holder and/or each participating Investor pro rata based on the number of shares such Holder and/or Investors would otherwise be entitled to sell to such Purchaser pursuant to this Section 3. The selling Holder or Investor shall use his or its reasonable best efforts to obtain the agreement of the Purchaser to the participation of the participating Investors in the contemplated sale, and shall not sell any Stock to such Purchaser if such Purchaser declines to permit the participating Investors to participate pursuant to the terms of this Section 3. The provisions of this Section 3 shall not apply to the sale of any Shares by a Holder to an Investor pursuant to an Offer under Section 2.

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4. Compliance with Securities Laws. To the extent that (i) the Investors and the Company do not exercise their rights under Section 2 or Section 3 with respect to any portion of the Offered Shares, and the transferring Holder intends to sell, assign, transfer or otherwise dispose of any Final Remaining Shares to the Purchaser, or (ii) the transferring Holder intends to effect a permitted transfer in accordance with Section 5 herein, then prior to any such proposed transfer or disposition of such Offered Shares, the holder or holders thereof shall provide the notice described in Section 2, and each such notice shall, if requested by the Company, be accompanied by an opinion of counsel satisfactory to the Company to the effect that the proposed transfer may be effected without registration under the Securities Act of 1933, as amended (the “Securities Act’) and any applicable state securities laws, whereupon, subject to any other restrictions on transfer contained herein, the holder of such stock shall be entitled to transfer such stock in accordance with the terms of its notice; provided, however, that no such opinion of counsel shall be required for (i) a transfer to one or more stockholders, partners or members of the transferor (in the case of a transferor that is a corporation, partnership or a limited liability company, respectively), (ii) a transfer to an affiliated corporation (in the case of a transferor that is a corporation) or (iii) a transfer to any Affiliate (as defined below) of any holder; provided, further, however, that any transferee other than a transferee receiving such shares for no consideration shall execute and deliver to the Company a representation letter in form reasonably satisfactory to the Company’s counsel to the effect that the transferee is acquiring such shares for its own account, for investment purposes and without any view to distribution thereof. Each certificate for Stock held by any Holder and transferred as above provided shall bear the legends in substantially the form set forth in Section 14.

For purposes of this Section 4, an “Affiliate” of any person means a person that, directly or indirectly, through one or more intermediaries, controls, is controlled by or is under common control with the first mentioned person. A person shall be deemed to control another person if such first person possesses, directly or indirectly, the power to direct, or cause the direction of, the management and policies of the second person, whether through the ownership of voting securities, by contract or otherwise. Without limiting the generality of the foregoing, with respect to an Investor, Affiliate shall also include any person or entity which, directly or indirectly, controls, is controlled by or is under common control with such Investor, including, without limitation, any general partner, officer or director of such Investor and any fund now or hereafter existing which is controlled by one or more general partners of, or shares the same management company as, such Investor.

5. Permitted Transfers. Anything herein to the contrary notwithstanding, the provisions of Sections 2 and 3 shall not apply to (but, for purposes of clarity, the provisions of Section 24 shall apply to): (a) any transfer of Shares to the Company by a Holder pursuant to Section 8 of this Agreement; (b) any sale or transfer by T-Online Venture Fund GmbH & Co. KG (“T- Venture”) to (i) Deutsche Telekom AG, (H) affiliates of Deutsche Telekom AG or T-Venture Holding GmbH within the meaning of § 15 German Stock Corporation Act (AktG) or (iii) funds managed or advised by T-Venture Holding GmbH; (c) any transfer of Shares by a Holder by gift or bequest or through inheritance to, or for the benefit of, any member or members of his or her immediate family (which shall include any spouse, children or grandchildren) or to a trust, partnership or limited liability company for the benefit of such Holder or such members of his or her immediate family; (d) any transfer of Shares by a Holder to a trust in respect of which he or

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she serves as trustee, provided that the trust instrument governing said trust shall provide that such Holder, as trustee, shall retain sole and exclusive control over the voting and disposition of said Shares until the termination of this Agreement; (e) any sale of Common Stock in a public offering pursuant to a registration statement filed by the Company with the Securities and Exchange Commission; and (f) any repurchase of shares of Common Stock by the Company from officers, employees, directors or consultants of the Company which are subject to restrictive stock purchase agreements under which the Company has the option to repurchase such shares at cost (or a lesser amount) upon the occurrence of certain events.

6. Election of Directors.

(a) Board Designation Rights; Initial Members. Each Holder hereby agrees to vote all of the Stock of the Company now owned or hereafter acquired by such party (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions (including, but not limited, to the nomination of specified persons, the execution of written consents and the calling of a stockholder meeting for the purpose of electing such specified persons) to cause and maintain the election to the Board of Directors of the Company, to the extent permitted pursuant to the Company’s Amended and Restated Certificate of Incorporation, as amended from time to time (the “Certificate of Incorporation”), the following:

(i) the then current Chief Executive Officer of the Company as one (1) of the Common Directors (as defined in the Certificate of Incorporation);

(ii) one (1) person designated by mutual agreement of Daniel Stephen Hafner and Paul English, as the other Common Director;

(iii) two (2) persons designated by the holders of at least seventy percent (70%) of the outstanding shares of the Series A Preferred Stock, voting as a separate class on an as-converted to Common Stock basis (the “Series A Designators”), as the two Series A Directors (as defined in the Certificate of Incorporation);

(iv) one (1) person designated by the holders of at least a majority of the outstanding shares of the Series C Stock, voting as a separate class (the “Series C Designators”), as the Series C Director (as defined in the Certificate of Incorporation);

(v) for so long as Sequoia Capital Growth Fund III or one or more of its affiliates (as defined in Rule 501 of Regulation D under the Securities Act) (“Sequoia”) holds at least 1,000,000 shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar event affecting the Preferred Stock), one (1) person designated by Sequoia as the Series D Director (as defined in the Certificate of Incorporation). In the event Sequoia does not hold at least 1,000,000 shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar event affecting the Preferred Stock), then, in lieu of Sequoia, the holders of at least a majority of the outstanding shares of the Series D Stock, voting as a separate class, shall be entitled to designate one (1) person as the Series D Director. The individual, entity, or group of individuals and/or entities who has the right to designate the Series D Director pursuant this Section 6(a)(v) shall be referred to herein as the “Series D Designator”; and

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(vi) one (1) person designated jointly by the Series A Designators, the Series C Designators, and the Series D Designator, each voting as a separate series, as the Remaining Director (as defined in the Certificate of Incorporation).

For the purposes of this Agreement, (x) “Stock” shall mean and include all Convertible Preferred Stock and all shares of Common Stock, and all other securities of the Company which may be exchangeable for, convertible into or issued in exchange for or in respect of shares of Common Stock (whether by way of stock split, stock dividends, combination, reclassification, reorganization or any other means), (y) “Board Designee” shall mean any individual who is designated for election to the Company’s Board of Directors pursuant to this Section 6; and (z) “Designator” or “Designators” shall mean, as applicable, any individual, entity, or group of individuals and/or entities who has the right to designate one (1) or more Board Designees for election to the Company’s Board of Directors pursuant to this Section 6.

(b) Removal: Successor Directors. In the absence of any designation from the appropriate Designator or Designators, the Board Designee previously designated by them and then serving shall be reelected if still eligible to serve as provided herein. From time to time during the term of this Agreement, a Designator or Designators may, in their sole discretion:

(i) elect to initiate the removal from the Company’s Board of Directors of any incumbent Board Designee who occupies a board seat for which such Designator or Designators are entitled to designate the Board Designee under Section 6(a), and/or

(ii) designate a new Board Designee for election to a board seat for which such Designator or Designators are entitled to designate the Board Designee under Section 6(a) (whether to replace a prior Board Designee or to fill a vacancy in such board seat); provided, however, that any new Board Designee designated by the Series A Designators, the Series C Designators and the Series D Designator for the Remaining Director must be ratified by the holders of a majority of the outstanding shares of Common Stock, which ratification may not be unreasonably withheld or delayed; provided further, however, no such ratification is required for any new Board Designee who has general experience with marketing and the travel related e-commerce industry.

In the event of an initiation of removal of a Board Designee pursuant to Section 6(b)(i), the Holders shall vote all of the Stock of the Company now owned or hereafter acquired by them (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions to cause the removal from the Company’s Board of Directors of the Board Designee or Designees so designated for removal by the appropriate Designator or Designators; provided, however, in no event shall any party vote to remove any Board Designee unless the appropriate Designator or Designators have so directed pursuant to Section 6(b)(i). In the event of designation of a Board Designee pursuant to Section 6(b)(i), the

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Holders shall vote all of the Stock of the Company now owned or hereafter acquired by them (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions to cause the election to the Company’s Board of Directors of any new Board Designee or Designees so designated for election to the Company’s Board of Directors pursuant to Section 6(b)(ii).

Without the consent of the Requisite Investors, the Holders hereby agree that they will not take any action, by vote or otherwise, to increase the authorized number of directors constituting the Company’s Board of Directors to more than seven (7) directors, unless the holders of Convertible Preferred Stock are then entitled to elect, in addition to the two (2) Series A Directors described in Section 6(a)(iii) above and one Series C Director described in Section 6(a)(iv) above, two additional Series A Directors and one additional Series C Director pursuant to Article 4B, subparagraph 6C of the Certificate of Incorporation (the “Additional Directors”), in which case the Company’s Board of Directors shall consist of no more than ten (10) members. If and for so long as the holders of Convertible Preferred Stock are entitled to elect the Additional Directors pursuant to Article 4B, subparagraph 6C of the Certificate of Incorporation, the Holders agree to vote all of the Stock of the Company now owned or hereafter acquired in favor of the election to the Board of Directors of two (2) persons designated from time to time by the Series A Designators and one (1) person designated from time to time by the Series C Designators.

7. Drag-Along Rights.

(a) lf (a) a majority of the members of the Company’s Board of Directors and (b) the Requisite Investors approve a sale of the Company or all or substantially all of the Company’s assets, whether by means of a merger, consolidation, sale of stock, sale of assets or otherwise (collectively, a “Sale of the Company”), all Holders shall consent to and vote their Shares in favor of the Sale of the Company, and if the Sale of the Company is structured as (i) a merger or consolidation of the Company, or a sale of all or substantially all of the Company’s assets, each Holder shall waive any dissenters’ rights, appraisal rights or similar rights in connection with such merger, consolidation or asset sale, or (ii) a sale of the stock of the Company, the Holders shall agree to sell their Shares on the terms and conditions approved by (x) a majority of the members of the Company’s Board of Directors and (y) the Requisite Investors; provided, however, that, (A) all proceeds from such Sale of the Company shall be payable to the holders of the Company’s capital stock in accordance with the Certificate of Incorporation, including, without limitation, Article 4B, Paragraph 3 thereof, which entitles the holders of Convertible Preferred Stock to a liquidation preference payment and other rights set forth therein, except that, at the discretion of the Company’s Board of Directors, holders of shares of Common Stock that are unvested on the date that the Sale of the Company is consummated may receive, in lieu of proceeds from the Sale of the Company and in exchange for their unvested shares of Common Stock, unvested securities or options to acquire securities of the entity surviving the Sale of the Company on an equitable basis, (B) except as set forth in the preceding clause (A), the terms of such Sale of the Company applicable to holders of shares of each series of Convertible Preferred Stock, in their capacities as holders thereof, shall be no less favorable than the terms applicable to the holders of all other series of Convertible Preferred Stock in their capacities as holders thereof and (C) if the Requisite Investors are given the option

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to choose the form of consideration to be received in such Sale of the Company on its Stock, the obligations of a Holder to approve the Sale of the Company under this Section 7 shall be conditioned upon such Holder having received the same option. Subject to the terms and conditions of Section 7(b), each Holder hereby irrevocably constitutes and appoints the Company and any representative or agent thereof with full power of substitution, as its true and lawful attorney-in-fact with full irrevocable power and authority in the place and stead of such Holder and in the name of such Holder or in its own name, for the purpose of carrying out the terms of this Section 7, to take any and all appropriate action and to execute any and all documents and instruments which may be necessary or desirable to accomplish the purposes of this Section 7. Such Holder hereby ratifies all that said attorneys shall lawfully do or cause to be done by virtue hereof.

(b) Notwithstanding the foregoing, a Holder will not be required to comply with Section 7(a) above (and the power of attorney as described in Section 7(a) shall not be effective or enforceable) in connection with any proposed Sale of the Company (the “Proposed Sale”) unless:

(i) the Company or any successor to, or assignee of, the Company complies with the provisions set forth in Section 8;

(ii) any representations and warranties to be made by such Holder in connection with the Proposed Sale are limited to representations and warranties related to authority, ownership and the ability to convey title to such Shares, including but not limited to representations and warranties that (w) the Holder holds all right, title and interest in and to the Shares such Holder purports to hold, free and clear of all liens and encumbrances, (x) the obligations of the Holder in connection with the transaction have been duly authorized, if applicable, (y) the documents to be entered into by the Holder have been duly executed by the Holder and delivered to the acquirer and are enforceable against the Holder in accordance with their respective terms and (z) neither the execution and delivery of documents to be entered into in connection with the transaction, nor the performance of the Holder’s obligations thereunder, will cause a breach or violation of the terms of any agreement, law or judgment, order or decree of any court or governmental agency;

(iii) the Holder shall not be liable for the inaccuracy of any representation or warranty made by any other Person in connection with the Proposed Sale, other than the Company (except to the extent that funds may be paid out of an escrow established to cover breach of representations, warranties and covenants of the Company as well as breach by any stockholder of any of identical representations, warranties and covenants provided by all stockholders);

(iv) the liability for indemnification, if any, of such Holder in the Proposed Sale and for the inaccuracy of any representations and warranties made by the Company in connection with such Proposed Sale, is several and not joint with any other Person (except to the extent that finds may be paid out of an escrow established to cover breach of representations, warranties and covenants of the Company as well as breach by any stockholder of any of identical representations, warranties and covenants provided by all stockholders), and is pro rata in proportion to the amount of consideration paid to such Holder in connection with such Proposed Sale (in accordance with the provisions of the Certificate of Incorporation);

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(v) liability shall be limited to such Holder’s applicable share (determined based on the respective proceeds payable to each Holder in connection with such Proposed Sale in accordance with the provisions of the Certificate of Incorporation) of a negotiated aggregate indemnification amount that applies equally to all Holders but that in no event exceeds the amount of consideration otherwise payable to such Holder in connection with such Proposed Sale, except with respect to claims related to fraud, the liability for which need not be limited as to such Holder; and

(vi) upon the consummation of the Proposed Sale, (w) each holder of each class or series of the Company’s stock will receive the same form of consideration for their shares of such class or series as is received by other holders in respect of their shares of such same class or series of stock, (x) each holder of a series of Convertible Preferred Stock will receive the same amount of consideration per share of such series of Convertible Preferred Stock as is received by other holders in respect of their shares of such same series, (y) each holder of Common Stock will receive the same amount of consideration per share of Common Stock as is received by other holders in respect of their shares of Common Stock, and (z) unless the Requisite Investors elect otherwise by written notice given to the Company at least ten (10) days prior to the effective date of any such Proposed Sale, the aggregate consideration receivable by all holders of the Convertible Preferred Stock and Common Stock shall be allocated among the holders of Convertible Preferred Stock and Common Stock on the basis of the relative liquidation preferences to which the holders of each respective series of Convertible Preferred Stock and the holders of Common Stock are entitled in a Liquidation Event (assuming for this purpose that the Proposed Sale is a Liquidation Event) in accordance with the Company’s Certificate of Incorporation in effect immediately prior to the Proposed Sale.

(c) Subject to Section 7(b)(vi) above, requiring the same form of consideration to be available to the holders of any single class or series of capital stock, if any holders of any capital stock of the Company are given an option as to the form and amount of consideration to be received as a result of the Proposed Sale, all holders of such capital stock will be given the same option.

8. Holder Put Right.

(a) Exercise of Put Right. Each Holder may, upon the terms and conditions set forth in this Section 8, require the Company to repurchase the shares of Common Stock acquired by such Holder pursuant to the Purchase Agreement (such shares, and any shares of the Company’s capital stock issued or issuable with respect to such shares by way of any stock split, stock dividend, reclassification, recapitalization or similar events, the “Put Shares”). To exercise such right, a Holder must deliver, during the Put Exercise Period (as defined below), a written notice to the Company (the “Put Election Notice”), which Put Election Notice must specify either that such Holder desires to sell all of such Holder’s Put Shares to the Company, or if a lesser number, the number of such Holder’s Put Shares that such Holder desires to sell to the Company. Subject to the terms and conditions hereof, the “Put Exercise Period” shall

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commence on the first to occur of the following dates, and shall terminate at the close of business, east coast time, on the thirtieth (30th) Business Day after such first date (subject to extension, for any individual Holder, pursuant to the provisions of this Section 8(a)), whether or not any of the other events specified in the following clauses occur subsequent to such first date:

(i) the date on which the Company consummates a Put Sale Event (as defined below) if such date occurs prior to June 30, 2011; or

(ii) the date that is thirty (30) days after the date that the Company consummates an underwritten public offering of Common Stock; or

(iii) June 30, 2011, if the Company has not consummated prior to such date an underwritten public offering of Common Stock.

For purposes of this Agreement, the following terms have the following meanings:

(1) “Put Sale Event” means either (A) the Company is sold by a sale of all or substantially all of its assets or of its capital stock (including, without limitation, by merger, consolidation or reorganization) to a Person or group of Affiliated Persons either in a single transaction or in a series of related transactions pursuant to which the Gross Per Share Consideration (as defined below) payable to holders of Common Stock in respect of their Put Shares is less than €13.33 per share (as adjusted for any stock split, stock dividend, reclassification. recapitalization or other similar event affecting the shares of Common Stock) or (B) a sale of all or substantially all of the assets of the Company and its subsidiaries, taken as a whole.

(2) “Gross Per Share Consideration” means the aggregate consideration payable in connection with a Put Sale Event to the extent that such consideration consists of cash and/or Freely Tradable Securities, calculated (x) without reduction for applicable taxes or indemnification obligations and (y) to include any portion thereof that is subject to any indemnity escrow or similar provision and (z) to exclude any portion thereof that consists of rights to future payment on account of any earn-outs, contingent payments and similar provisions.

(3) “Freely Tradable Securities” means any securities that are (A) (x) listed for trading on a recognized United States or non-United States national or regional securities exchange or (y) reported through any recognized United States or non-United States automated quotation system and (B) not subject to restrictions on transfer as a result of contractual provisions (excluding restrictions resulting from any indemnity escrow arrangement or similar restriction thereon). For purposes of this Agreement. the value of Freely Tradable Securities shall be deemed to be the average of the closing prices of such securities on the securities exchange or quotation system on which they are primarily traded over the twenty (20) trading days preceding the Put Sale Event.

In the event that the Company has not delivered a written notice to any Holder regarding the occurrence of any of the events described in Sections 8(a)(i) or 8(a)(ii) within five Business Days

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after the occurrence of any such event, then the Put Exercise Period for such Holder shall be automatically extended by the number of days equal to the difference between (x) such fifth Business Day and (y) the date on which the Company delivered such written notice to such Holder (or, in connection with a Qualified Put Sale Event (as defined below), the earlier of such date and the date on which such Holder received any of the Transaction Proceeds (as defined below) with respect thereto). The delivery by a Holder during the Put Exercise Period (as so extended, if applicable) of a Put Election Notice pursuant to this Section 8 shall be deemed to constitute a valid, legally binding and enforceable agreement for the sale by the Holder and purchase by the Company of all of such Holder’s Put Shares (or such lesser number of Put Shares if so specified in such Put Election Notice), at a purchase price per share equal to the Repurchase Price (as defined below).

(b) Repurchase Price. The per share price at which the Company shall repurchase the Put Shares in connection with any Put Election Notice (the “Repurchase Price”) shall be €13.33 per share (as adjusted for any stock split, stock dividend, reclassification, recapitalization or other similar event affecting the shares of Common Stock). The Repurchase Price shall be payable in Euros.

(c) Qualified Put sale Events. Notwithstanding anything to the contrary set forth in this Agreement, in the event that a Put Exercise Period commences with respect to a Put Sale Event that is structured as a purchase of the Company’s capital stock or as a merger, combination, corporate reorganization or similar transaction (such Put Sale Event is referred to as a “Qualified Put Sale Event”), each Holder shall have the right to put back to the Company during such Put Exercise Period all, or a lesser portion, of the consideration received by each Holder in connection with such Qualified Put Sale Event (such proceeds, whether in the form of cash, securities, other property and/or rights to receive any of the foregoing, are collectively referred to as the “Transaction Proceeds”) in exchange for a cash payment equal the product of (i) the Repurchase Price multiplied by (ii) the number of Put Shares held by such Holder immediately prior to the closing of such Qualified Put Sale Event; provided, that, such payment shall be appropriately adjusted if such Holder desires to exchange less than all of such Holder’s Transaction Proceeds. To exercise the put right described in the immediately preceding sentence, a Holder must deliver, during the Put Exercise Period, a written notice to the Company (the “Put Back Right Notice”), which Put Back Right Notice specifies that the Holder wishes to deliver all, or a lesser portion, of the Transaction Proceeds received by such Holder in the Qualified Put Sale Event in exchange for the cash payment described in the immediately preceding sentence. The delivery by a Holder of a Put Back Right Notice pursuant to this Section 8(c) shall be deemed to constitute a valid, legally binding and enforceable agreement for the exchange between the Holder and the Company of the Transaction Proceeds, or such lesser amount actually delivered, by a Holder in exchange for a cash payment equal to the amount described in the first sentence of this Section 8(c).

(d) Closing. Any closing pursuant to this Section 8 (with respect to each applicable Holder, a “Put Closing”) shall take place remotely via the exchange of documents and signatures at such date and time as shall be agreed upon by the Company and the Holder delivering such Put Election Notice or Put Back Right Notice, as applicable, but in no event later than the twentieth (20th) Business Day after the last day of the Put Exercise Period (as extended,

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if applicable). At each Put Closing, the applicable Holder participating in such closing shall deliver to the Company a certificate representing the number of Put Shares being repurchased from such Holder by the Company or the amount of Transaction Proceeds being exchanged between such Holder and the Company, as applicable, at such closing, against payment of the Repurchase Price therefor either by (x) check or wire transfer of immediately available funds payable and delivered to such Holder with respect to any Put Shares which are then not held in the Indemnity Escrow Account or (y) check or wire transfer of immediately available funds payable and delivered to the Escrow Agent for credit to such Holder’s escrowed cash account with respect to any Put Shares which are then held in the Escrow Account.

(e) Miscellaneous. The Company shall not, by amendment to the Certificate of Incorporation (whether by way of merger, operation of law, or otherwise) or through any drag-along or other reorganization, transfer of assets, consolidation, merger, dissolution, issuance or sale of securities, agreement or any other action, avoid or seek to avoid the observance or performance of any of the terms to be observed or performed in this Section 8 by the Company and shall at all times in good faith assist in the carrying out of all the provisions of this Section 8. As a condition precedent to any Qualified Put Sale Event which causes a Put Exercise Period to commence, the Company shall cause each Person acquiring the Company in such Qualified Put Sale Event to agree in writing to be bound by the terms and conditions of this Agreement, to respect the rights of the Holders under this Section 8 and to perform the Company’s obligations under this Section 8, including without limitation, delivery to each Holder of any notices required by this Section 8.

9. Information Rights.

(a) The Company shall furnish the following information to each Holder upon request:

(i) Quarterly Reports: once available after the end of any of the first three quarters of any fiscal year of the Company, unaudited financial statements of the Company and its Subsidiaries with respect to such quarter as of the end of such quarter, including therein consolidated balance sheets of the Company and its Subsidiaries as of the end of such quarter and consolidated statements of income of the Company and its Subsidiaries for such quarter, setting forth in each case in comparative form the corresponding figures for the corresponding period of the preceding fiscal year, prepared in accordance with generally accepted accounting principles consistently applied (subject to year-end audit adjustments);

(ii) Annual Reports: once available after the end of each fiscal year of the Company, a copy of the annual audit report for such year for the Company and its Subsidiaries, including therein consolidated balance sheets of the Company and its Subsidiaries as of the end of such fiscal year and consolidated statements of income of the Company and its Subsidiaries for such fiscal year, setting forth in each case in comparative form the corresponding figures for the preceding fiscal year, all such consolidated statements to be prepared in accordance with generally accepted accounting principles consistently applied; and

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(iii) Other Information: such other historical financial information respecting the business or condition of the Company and its Subsidiaries as such Holder may from time to time reasonably request.

(b) Each Holder hereby covenants and agrees that all of the information disclosed to such Holder pursuant to the provisions of Section 9(a) will be kept confidential and such Holder will not disclose or divulge any such information unless such information is or becomes publicly known without violation of this provision by such Holder, or unless the Company gives its written consent to such Holder to release such information; provided, however, that a Holder may disclose confidential information (i) to its attorneys, accountants, consultants, and other professionals to the extent such persons are bound by a duty of confidentiality or similar ethical obligation and solely to the extent necessary to obtain their services in connection with monitoring its investment in the Company or (ii) as may otherwise be required by law, provided that the Holder promptly notifies the Company of such disclosure and takes reasonable steps to minimize the extent of any such required disclosure, and provided further that such Holder shall be responsible for any further disclosure by any person specified in the preceding clause (i) to the extent such further disclosure would have been a violation of this provision if made directly by such Holder. Notwithstanding the foregoing, nothing in this Section 9(b) shall in any way limit the confidentiality obligations of officers or employees of the Company pursuant to the terms of any employment, non-disclosure or similar agreement with the Company.

10. Termination. This Agreement, and the respective rights and obligations of the parties hereto, shall terminate upon the completion of a firm commitment underwritten public offering of Common Stock in which (a) the aggregate gross proceeds received by the Company shall be at least $25,000,000, and (b) the per share price paid by the public for such shares shall be at least $31.09 (appropriately adjusted to reflect any subdivision or combination of the Common Stock occurring after the date hereof) (a “Qualified Public Offering”); provided, however, that (x) Sections 1 through 3 shall terminate on the earlier of (i) the completion of a Qualified Public Offering and (ii) ten (10) years after the date hereof (y) Section 8 shall terminate pursuant to the terms as set forth therein and (z) Section 9(a) shall terminate upon the completion of a firm commitment underwritten public offering of Common Stock by the Company.

11. Notices. Any notices or other communication required to be sent or given hereunder by any of the parties shall in every case be in writing and shall be deemed properly served if (a) delivered personally, (b) sent by certified U.S. Mail, with first class postage prepaid, return receipt requested, (c) delivered by a recognized overnight courier service, with certification of receipt requested, or (d) sent by facsimile transmission with a confirmation copy sent by overnight courier, in each case, to the parties at the addresses and telecopy numbers as set forth below or at such other addresses or telecopy number as may be furnished in writing by any party pursuant to this Section 11 (except that notices of changes of address or a telecopy number shall only be effective upon receipt):

if to the Company or any Holder as of the date of the Agreement, at the address of such party set forth in the Purchase Agreement, with a copy sent to such party’s legal counsel designated in the Purchase Agreement, if applicable;

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if to any Investor as of the date of the Agreement, to such party at its address set forth on Schedule I hereto, or the address reflected on the books and records of the Company if such Investor has provided notice to the Company of any change of address subsequent to the date hereof;

if to a Holder who subsequently becomes a party to this Agreement, at its address set forth on the Instrument of Accession pursuant to which such Holder became a party to this Agreement; and

if to a party who subsequently becomes an Investor, at its address set forth on the Instrument of Accession pursuant to which such Investor became a party hereto.

Date of service of such notice shall be (w) the date such notice is personally delivered, (x) three (3) days after the date of mailing if sent by certified U.S. mail, (y) two (2) days after date of delivery to the overnight courier if sent by overnight courier (as evidenced by a written receipt from the courier), or (z) the next succeeding business day after transmission by facsimile.

12. Failure to Deliver Shares. If a Holder becomes obligated to sell any Shares owned by, or held for the benefit of, such Holder to an Investor, a Qualified Transferee or the Company under this Agreement and fails to deliver such shares in accordance with the terms of this Agreement, such Investor, Qualified Transferee or the Company, as applicable, may, at its option, in addition to all other remedies it may have, send to the Company (or in the case of the Company, retain) for the benefit of such Holder the purchase price for such Shares as is herein specified. Thereupon, the Company upon written notice to said Holder, (a) shall cancel on its books the certificate(s) representing the shares to be sold and (b) if applicable shall issue, in lieu thereof, in the name of such Investor or Qualified Transferee, a new certificate(s) representing such Shares, and thereupon all of said Holder’s rights in and to such shares shall terminate. If a Holder transfers any Shares to a Purchaser in violation of this Agreement, the Company may, at the election of a majority of the disinterested members of the Company’s Board of Directors, cancel on the books of the Company any shares of capital stock then held by such Holder, and any such breaching Holder agrees to purchase from the Purchasers and any transferee a number of shares of capital stock equal to the amount so transferred in violation of this Agreement.

13. Specific Performance; Proxy. The rights of the parties under this Agreement are unique and, accordingly, the parties shall, in addition to such other remedies as may be available to any of them at law or in equity, have the right to enforce their rights hereunder by actions for specific performance to the extent permitted by law. The voting of shares of capital stock pursuant to this Agreement may be effected in person, by proxy, by written consent or in any other manner permitted by applicable law. Each Holder hereby grants to the Secretary of the Company, in the event that such Holder fails to vote its shares of capital stock as required by Section 6 or Section 7 hereof, a proxy coupled with an interest in all Shares owned by such Holder empowering the Secretary to vote such Shares as to such matters as are set forth in Section 6 or Section 7 hereof, which proxy is irrevocable until this Agreement terminates pursuant to its terms or this Section 13 is amended to remove such grant of proxy in accordance with Section 18 of this Agreement.

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14. Restrictive Legends. Each certificate representing Stock issued to the Holders shall, except as otherwise provided herein, be stamped or otherwise imprinted with legends substantially in the following form:

“THE SALE, PLEDGE, HYPOTHECATION OR TRANSFER OF THE SECURITIES REPRESENTED BY THIS CERTIFICATE IS SUBJECT TO, AND IN CERTAIN CASES PROHIBITED BY, THE TERMS AND CONDITIONS OF STOCKHOLDERS’ AGREEMENT, DATED AS OF MAY 6, 2010 BY AND AMONG THE COMPANY AND CERTAIN STOCKHOLDERS PARTIES THERETO, AS MAY BE AMENDED FROM TIME TO TIME (THE “STOCKHOLDERS’ AGREEMENT”). THE SECURITIES EVIDENCED HEREBY ARE ALSO SUBJECT TO CERTAIN VOTING AGREEMENTS, RESTRICTIONS AND PROXIES CONTAINED IN THE STOCKHOLDERS’ AGREEMENT. COPIES OF THE STOCKHOLDERS’ AGREEMENT MAY BE OBTAINED UPON WRITTEN REQUEST TO THE SECRETARY OF THE COMPANY. BY ACCEPTING ANY INTEREST IN SUCH SECURITIES THE PERSON ACCEPTING SUCH INTEREST SHALL BE DEEMED TO AGREE TO AND SHALL BECOME BOUND BY ALL THE PROVISIONS OF THAT STOCKHOLDERS’ AGREEMENT, INCLUDING THE VOTING PROVISIONS AND RESTRICTIONS ON TRANSFER AND OWNERSHIP SET FORTH THEREIN”

“THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE SECURITIES LAWS AND MAY NOT BE TRANSFERRED OR OTHERWISE DISPOSED OF UNLESS IT HAS BEEN REGISTERED OR QUALIFIED UNDER SUCH ACT AND APPLICABLE STATE SECURITIES LAWS OR AN EXEMPTION FROM REGISTRATION OR QUALIFICATION IS AVAILABLE UNDER SUCH ACT AND STATE SECURITIES LAWS.”

A certificate shall not bear the last of such legends if in the opinion of counsel satisfactory to the Company all the securities represented thereby may be publicly sold without registration under the Securities Act, and any applicable state securities laws.

15. Representations and Warranties. The Company and each Holder represents and warrants to each other as follows:

(a) The execution, delivery and performance of this Agreement by such party has been duly authorized by all requisite corporate action (in the case of the Company or Holders that are not individuals) and will not violate any provision of law, any order of any court or other agency of government, by-laws or other governing document (in the case of a party that is not an individual) or any provision of any indenture, agreement or other instrument to which such party or any or its properties or assets is bound, conflict with, result in a breach of or constitute (with due notice or lapse of time or both) a default under any such indenture, agreement or other instrument of such party or, in the case of the Company, result in the creation or imposition of any lien, charge or encumbrance of any nature whatsoever upon any of the properties or assets of the Company.

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(b) This Agreement has been duly executed and delivered by such party and constitutes the legal, valid and binding obligation of such party, enforceable in accordance with its terms subject, as to enforcement of remedies, to applicable bankruptcy, insolvency, moratorium, reorganization and similar laws affecting creditors’ rights generally and to general equitable principles.

16. Entire Agreement. This Agreement and the Purchase Agreement (including any and all exhibits, schedules and other instruments contemplated thereby) constitute the entire agreement among the parties with respect to the subject matter hereof and supersede all prior agreements or understandings between them or any of them as to such subject matter.

17. Waivers and Further Agreements. Any provision of this Agreement may be waived by an instrument in writing executed and delivered by (i) the Requisite Investors and (ii) the Holders holding at least two-thirds of the Shares held by the Holders (which must include T-Venture), in the aggregate (calculated on an as-converted to Common Stock basis). Any waiver by any party of a breach of any provision of this Agreement shall not operate or be construed as a waiver of any subsequent breach of that provision or of any other provision hereof. Each of the parties hereto agrees to execute all such further instruments and documents and to take all such further action as any other party may reasonably require in order to effectuate the terms and purposes of this Agreement. Notwithstanding the foregoing, no waiver may treat one Investor more adversely than any other Investor, or treat one Holder more adversely than any other Holder, without the consent of such Investor or Holder, respectively, adversely affected by such waiver (ignoring for these purposes any disparity resulting solely from the fact that the various parties hereto hold different numbers of shares of Stock).

18. Amendments. Except as otherwise expressly provided herein, any provision of this Agreement may be amended pursuant to an instrument in writing executed and delivered by (a) the Holders holding at least two-thirds of the Shares held by the Holders (which must include T-Venture), in the aggregate (calculated on an as-converted to Common Stock basis), (b) the Company and (c) the Requisite Investors. Notwithstanding the foregoing, (i) no amendment may treat one Investor more adversely than any other Investor without the consent of such Investor adversely affected by such amendment (ignoring for these purposes any disparity resulting solely from the fact that the various Investors hold different numbers of shares of Stock), (ii) no amendment may treat one Holder more adversely than any other Holder without the consent of such Holder (ignoring for these purposes any disparity resulting solely from the fact that the various Holders hold different numbers of shares of Stock), (iii) no amendment, waiver or modification to the rights of a Designator to appoint or remove a Board Designee pursuant to Section 6 shall be effective without the consent of such Designator, (iv) the Company may unilaterally amend Schedule I and/or Exhibit A hereto as required to reflect any changes in the number of shares of Stock of the Company held by any Holder or Investor, or the addition of new Holders or Investors as contemplated by Section 24 and (v) the provisions of Section 6 hereof (and any defined term appearing therein) may be amended or modified from time to time by an instrument in writing executed by the Company and the Requisite Investors.

19. Assignment: Successors and Assigns. This Agreement shall be binding upon and shall inure to the benefit of the parties hereto and their respective heirs, executors, legal representatives, successors and permitted transferees, except as may be expressly provided otherwise herein.

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20. Severability. In case any one or more of the provisions contained in this Agreement shall for any reason be held to be invalid, illegal or unenforceable in any respect, such invalidity, illegality or unenforceability shall not affect any other provision of this Agreement and such invalid, illegal and unenforceable provision shall be reformed and construed so that it will be valid, legal, and enforceable to the maximum extent permitted by law.

21. Counterparts. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

22. Section Headings. The headings contained in this Agreement are for reference purposes only and shall not in any way affect the meaning or interpretation of this Agreement.

23. Governing Law. This Agreement shall be construed and enforced in accordance with and governed by the laws of the General Corporation Law of the State of Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to its principles of conflicts of laws.

24. Additional Parties. Unless otherwise consented to by the Board of Directors, and other than a transfer pursuant to clause (a), (e) or (f) of Section 5, any transferee of Stock held by a Holder shall become a party to this Agreement by executing and delivering to the Company an executed Instrument of Accession in the form of Schedule II hereto. Upon such execution and delivery, such transferee shall be deemed to be a “Holder” hereunder with all of the rights and obligations thereof. The Company may, from time to time, allow one or more third parties to become Investors hereunder upon the execution and delivery to the Company of an executed Instrument of Accession in the form of Schedule II hereto by such third party, whereupon such third party shall be deemed to be an “Investor” hereunder with all of the rights and obligations thereof.

25. Acknowledgement. Notwithstanding anything to the contrary set forth in this Agreement, any obligations of the Holders pursuant to this Agreement shall be made severally, and not jointly, by each Holder as to itself, himself or herself only, and any Holder who has breached any such obligation as to itself, himself or herself shall be liable with respect to all losses as a result of a breach thereof.

26. Currency. References to “Euro” and “€” mean euro in the lawful currency of the European Union.

[signature pages follow]

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IN WITNESS WHEREOF, the undersigned have executed this Stockholder Agreement as a sealed instrument as of the day and year first above written.

COMPANY:
KAYAK SOFTWARE CORPORATION
By:     /s/ Daniel Stephen Hafner
Name:	Daniel Stephen Hafner
Title:	Chief Executive officer

[The remainder of this page is intentionally left blank.]

[Signature Page to Stockholders’ Agreement]

INVESTORS:

GENERAL CATALYST GROUP II, L.P.		GENERAL CATALYST GROUP III, L.P.
By:	General Catalyst Partners II, L.P.	By:	General Catalyst Partners III, L.P.
Its General Partner		Its General Partner
By:	General Catalyst GP II, LLC	By:	General Catalyst GP III, LLC
Its General Partner		Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald	Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer	Title:	Member and Chief Financial Officer
GC ENTREPRENEURS FUND II, L.P.		GC ENTREPRENEURS FUND III, L.P.
By:	General Catalyst Partners II, L.P.	By:	General Catalyst Partners III, L.P.
Its General Partner		Its General Partner
By:	General Catalyst GP II, LLC	By:	General Catalyst GP III, LLC
Its General Partner		Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald	Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer	Title:	Member and Chief Financial Officer
GENERAL CATALYST GROUP V, L.P.		GC ENTREPRENEURS FUND V, L.P.
By:	General Catalyst Partners V, L.P.	By:	General Catalyst Partners V, L.P.
Its General Partner		Its General Partner
By:	General Catalyst GP V, LLC	By:	General Catalyst GP V, LLC
Its General Partner		Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald	Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer	Title:	Member and Chief Financial Officer

[Signature Page to Stockholders’ Agreement]

GENERAL CATALYST GROUP V
SUPPLEMENTAL, L.P.
By:	General Catalyst Partners V, L.P.
Its General Partner
By:	General Catalyst GP V, LLC
Its General Partner
By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer

[Signature Page to Stockholders’ Agreement]

  /s/ Daniel Stephen Hafner

 Daniel Stephen Hafner

  /s/ Paul English

 Paul English

[Signature Page to Stockholder’ Agreement]

ACCEL LONDON II L.P.
By:	Accel London II Associates L.P.
Its: General Partner
By:	Accel London II Associates L.L.C.
Its: General Partner
By:	/s/ JONATHAN BIGGS
	Name:	JONATHAN BIGGS
	Title:	Attorney in Fact
ACCEL LONDON INVESTORS 2006 L.P
By:	Accel London II Associates L.L.C
Its General Partner
By:	/s/ JONATHAN BIGGS
	Name:	JONATHAN BIGGS
	Title:	Attorney in Fact

[Signature Page to Stockholders’ Agreement]

SEQUOIA CAPITAL XI
SEQUOIA TECHNOLOGY PARTNERS XI
SEQUOIA CAPITAL XI PRINCIPALS
FUND
By:	SC XI Management, LLC
A Delaware Limited Liability Company
General Partner of Each
By:	/s/ Michael Moritz

Name:
Title:	Managing Member
SEQUOIA CAPITAL GROWTH FUND III
SEQUOIA CAPITAL GROWTH PARTNERS III
SEQUOIA CAPITAL GROWTH III PRINCIPALS FUND
By:	SCGF III Management, LLC
	A Delaware Limited Liability Company
	General Partner of Each
By:	/s/ Michael Moritz

Name:
Title:	Managing Member

Page 23 of 33

[SIGNATURE PAGE TO STOCKHOLDERS’ AGREEMENT]

OAK INVESTMENT PARTNERS XII, LIMITED PARTNERSHIP

By:    Oak Associates XII, LLC, its General Partner

By:   /s/ Iftikar A. Ahmed

Name:	Iftikar A. Ahmed
Title:	Managing Member

[Signature Page to Stockholders’ Agreement]

HOLDERS:

  /s/ Matthias Zahn, i.V. Stefan Sebastiani

Matthias Zahn, i.V. Stefan Sebastiani

/s/ Wolfgang Heigl

Wolfgang Heigl

/s/ Bernhard von Mellenthin i.V. Stefan Sebastiani

Bernhard von Mellenthin i.V. Stefan Sebastiani

/s/ Lars Jankowfsky

Lars Jankowfsky

/s/ Andreas Stegmann, i.V. S. Sebastiani

Andreas Stegmann, i.V. S. Sebastiani

/s/ Pierre Jacoby-Schrade, i.V. S. Sebastiani

Pierre Jacoby-Schrade, i.V. S. Sebastiani

/s/ Christian Saller, i.V. S. Sebastiani

Christian Saller, i.V. S. Sebastiani

T-Online Venture Fund GmbH & Co. KG

By:	/s/ (illegible)
Name:	(illegible)
Title:
Mayflower GmbH
By:	/s/ i.V. S. Sebastiani
Name:	i.V. S. Sebastiani
Title:

Page 26 of 33

[SIGNATURE PAGE TO STOCKHOLDERS’ AGREEMENT]

SCHEDULE I

KAYAK SOFTWARE CORPORATION

SCHEDULE OF HOLDERS AND INVESTORS

Investors:

General Catalyst Group II, L.P.

GC Entrepreneurs Fund II, L.P.

General Catalyst Group III, L.P.

GC Entrepreneurs Fund III, L.P.

General Catalyst Group V, L.P.

General Catalyst Group V Supplemental, L.P.

GC Entrepreneurs Fund V, L.P.

20 University Road, Suite 450

Cambridge, MA 02138

Fax: (617) 234-7040

Attn: Joel Cutler

Daniel Stephen Hafner

1316 Pequot Avenue

Southport, CT 06890

Fax: (203) 899-3125

Paul English

204 Pleasant Street

Arlington, MA 02476

Sequoia Capital Growth Fund III

Sequoia Capital Growth Partners III

Sequoia Capital Growth III Principals Fund

Sequoia Capital XI

Sequoia Technology Partners XI

Sequoia Capital XI Principals Fund

3000 Sand Hill Road

Bldg 4, Suite 180

Menlo Park, CA 94025

Oak Investment Partners XII, Limited Partnership

One Gorham Island

Westport, CT 06880

Attu: Iftikar A. Ahmed

Investors:

Accel London II, L.P.

Accel London Investors 2006 L.P.

428 University Avenue

Palo Alto, CA 94301-1812

Fax: (650) 614-4880

Attn: Richard Zamboldi

Notices also sent to

16 St. James’s Street

London SWIA IER

United Kingdom

Fax: +44 (0) 20 7170 1099

Attn: Jonathan Biggs

Attn: Harry Nelis

Holders:

Wolfgang Heigl

Hainstrabe 29,

86830 Schwabmunchen

Germany

Lars Jankowfsky

Elsenheimerstr. 20,

80687 Munich

Germany

Christian Saller

Maximilianstrabe 22,

80539 München

Germany

Pierre Jacoby-Schrade

Sternwaldstrabe 26,

79102 Freiburg

Germany

Andreas Stegmann

Hochvogelstrabe 7,

86163 Augsburg

Germany

Bernhard von Mellenthin

Am Kehlfeld 6,

82266 Inning am Ammersee

Germany

Matthias Zahn

Bandelstrabe 24

80638 München

Germany

Holders:

Mayflower GmbH

Mannhardtstral3e 6,

80538 Munich

Germany

(registered with the commercial register of the Local Court (Amtsgericht) Munich under registration number HRB 142039)

T-Online Venture Fund GmbH & Co. KG

Gotenstrabe 156,

53175 Bonn

Germany

(registered with the commercial register of the Local Court (Amtsgericht) Bonn under HRA 4847)

SCHEDULE II

KAYAK SOFTWARE CORPORATION

INSTRUMENT OF ACCESSION FOR HOLDER

The undersigned,                                         , as a condition precedent to becoming the owner or holder of record of                                          (            ) shares of the                          stock, par value $0.001 per share, of Kayak Software Corporation, a Delaware corporation (the “Company”), or options to purchase such stock, hereby agrees to become a Holder under that certain Stockholders’ Agreement dated as of May , 2010 by and among the Company and other stockholders of the Company party thereto (the “Agreement”). This Instrument of Accession shall take effect and shall become an integral part of, and the undersigned shall become a party to and bound by, said Stockholders’ Agreement immediately upon execution and delivery to the Company of this Instrument of Accession.

The undersigned represents and warrants that (a) it will acquire the Common Stock to be acquired by it for its own account and that the Common Stock is being and will be acquired by it for the purpose of investment and not with a view to distribution or resale thereof; (b) it has substantial experience in evaluating and investing in private placement transactions of securities in companies similar to the Company so that it is capable of evaluating the merits and risks of its investment in the Company and has the capacity to protect its own interests; and is able to bear the economic risks of an investment in the Common Stock, and at the present time could afford a complete loss of such investment; (c) if an entity, (i) it is duly organized and validly existing under the laws of the state of its formation; (ii) it has the necessary corporate or other power and authority, and has taken all necessary applicable action for the authorization, execution and delivery of and the performance of its obligations under, the Agreement, (d) this Instrument of Accession has been duly executed and delivered by, and constitutes valid, legal, binding and enforceable agreement of, the undersigned, and (e) neither the execution of this Instrument of Accession nor the undertaking of the obligations contained in the Agreement will (i) violate any provision of the organizational documents of the undersigned, if an entity, or (ii) violate or conflict with or result in a breach of any provision of any law, statute, rule, regulation, order, permit, judgment, injunction, decree or other decision of any court or other tribunal or any governmental entity or agency binding on the undersigned. The acquisition by the undersigned of the Common Stock acquired by it shall constitute a confirmation of the representations and warranties made by it as of the date of such acquisition.

[Signature Page Follows)

IN WITNESS WHEREOF, this INSTRUMENT OF ACCESSION has been duly executed by or on behalf of the undersigned as of the date below written.

Signature:

(Print Name)

Address:

Date:

Accepted:

KAYAK SOFTWARE CORPORATION

By:

  Name:

  Title:

Date:

SCHEDULE III

KAYAK SOFTWARE CORPORATION

INSTRUMENT OF ACCESSION FOR INVESTOR

The undersigned,                                         , as a holder of record of                                          (            ) shares of the                      stock, par value $0.001 per share, of Kayak Software Corporation, a Delaware corporation (the “Company”), hereby agrees to become an Investor under that certain Stockholders’ Agreement dated as of                          , 20W by and among the Company and other stockholders of the Company party thereto (the “Agreement”). This Instrument of Accession shall take effect and shall become an integral part of, and the undersigned shall become a party to and bound by, said Stockholders’ Agreement immediately upon execution and delivery to the Company of this Instrument of Accession.

IN WITNESS WHEREOF, this INSTRUMENT OF ACCESSION has been duly executed by or on behalf of the undersigned as of the date below written.

Signature:

(Print Name)

Address:

Date:

Accepted:

KAYAK SOFTWARE CORPORATION

By:

  Name:

  Title:

Date:

EXHIBIT A

HOLDER SHARES

Holder	Shares	Shares Held in Escrow	Shares Subject to Holdback
T-Online Venture Fund GmbH & Co. KG	237,262	—	—
Wolfgang Heigl	97,761	30,028	14,799
Lars Jankowfsky	56,781	17,440	8,595
Christian Saller	44,499	13,668	6,736
Pierre Jacoby-Schrade	21,567	5,753	—
Andreas Stegmann	112,560	30,028	—
Bernhard von Mellenthin	2,025	540	—
Matthias Zahn	82,229	21,936	—
Mayflower GmbH	16,330	4,357	—
Total:	671,114	123,750	30,130

EX-4.7

Exhibit 4.7

AMENDMENT NO. 1 TO STOCKHOLDERS’ AGREEMENT

THIS AMENDMENT NO. 1 TO STOCKHOLDERS’ AGREEMENT, dated as of December 22, 2011 (this “Amendment”), hereby amends that certain Stockholders’ Agreement, dated as of May 6, 2010, by and among KAYAK Software Corporation (the “Company”) and the other parties thereto (the “Stockholders’ Agreement”). Capitalized terms used but not otherwise defined herein shall have the meanings provided in the Stockholders’ Agreement.

W I T N E S S E T H

WHEREAS, the Company and the Requisite Investors have mutually agreed to amend and restate Section 6 of the Stockholders’ Agreement in its entirety;

NOW, THEREFORE, for good and valuable consideration, the receipt and legal sufficiency of which is hereby acknowledged, Section 6 of the Stockholders’ Agreement hereby is amended and restated to read in its entirety as follows:

“6. Election of Directors.

(a) Board Designation Rights; Initial Members. Each Holder hereby agrees to vote all of the Stock of the Company now owned or hereafter acquired by such party (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions (including, but not limited, to the nomination of specified persons, the execution of written consents and the calling of a stockholder meeting for the purpose of electing such specified persons) to cause and maintain the election to the Board of Directors of the Company, to the extent permitted pursuant to the Company’s Amended and Restated Certificate of Incorporation, as amended from time to time (the “Certificate of Incorporation”), the following:

(i) the then current Chief Executive Officer of the Company as one (1) of the Common Directors (as defined in the Certificate of Incorporation);

(ii) one (1) person designated by mutual agreement of Daniel Stephen Hafner and Paul English, as the other Common Director;

(iii) two (2) persons designated by the holders of at least seventy percent (70%) of the outstanding shares of the Series A Preferred Stock, voting as a separate class on an as-converted to Common Stock basis (the “Series A Designators”), as the two Series A Directors (as defined in the Certificate of Incorporation);

(iv) one (1) person designated by the holders of at least a majority of the outstanding shares of the Series C Stock, voting as a separate class (the ‘‘Series C Designators”), as the Series C Director (as defined in the Certificate of Incorporation);

Page 1 of 18

(v) for so long as Sequoia Capital Growth Fund III or one or more of its affiliates (as defined in Rule 501 of Regulation D under the Securities Act) (“Sequoia”) holds at least 1,000,000 shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar event affecting the Preferred Stock), one (1) person designated by Sequoia as the Series D Director (as defined in the Certificate of Incorporation). In the event Sequoia does not hold at least 1,000,000 shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar event affecting the Preferred Stock), then, in lieu of Sequoia, the holders of at least a majority of the outstanding shares of the Series D Stock, voting as a separate class, shall be entitled to designate one (1) person as the Series D Director. The individual, entity, or group of individuals and/or entities who has the right to designate the Series D Director pursuant this Section 6(a)(v) shall be referred to herein as the “Series D Designator”;

(vi) one (1) person designated jointly by the Series A Designators, the Series C Designators, and the Series D Designator, each voting as a separate series, as the Preferred and Common Director (as defined in the Certificate of Incorporation); and

(vii) one (1) additional person designated jointly by the Series A Designators, the Series C Designators, and the Series D Designator, each voting as a separate series, as the Remaining Director (as defined in the Certificate of Incorporation).

For the purposes of this Agreement, (x) “Stock” shall mean and include all Convertible Preferred Stock and all shares of Common Stock, and all other securities of the Company which may be exchangeable for, convertible into or issued in exchange for or in respect of shares of Common Stock (whether by way of stock split, stock dividends, combination, reclassification, reorganization or any other means), (y) “Board Designee” shall mean any individual who is designated for election to the Company’s Board of Directors pursuant to this Section 6; and (z) “Designator” or “Designators” shall mean, as applicable, any individual, entity, or group of individuals and/or entities who has the right to designate one (1) or more Board Designees for election to the Company’s Board of Directors pursuant to this Section 6.

(b) Removal; Successor Directors. In the absence of any designation from the appropriate Designator or Designators, the Board Designee previously designated by them and then serving shall be reelected if still eligible to serve as provided herein. From time to time during the term of this Agreement, a Designator or Designators may, in their sole discretion:

Page 2 of 18

(i) elect to initiate the removal from the Company’s Board of Directors of any incumbent Board Designee who occupies a board seat for which such Designator or Designators are entitled to designate the Board Designee under Section 6(a), and/or

(ii) designate a new Board Designee for election to a board seat for which such Designator or Designators are entitled to designate the Board Designee under Section 6(a) (whether to replace a prior Board Designee or to fill a vacancy in such board seat); provided, however, that any new Board Designee designated by the Series A Designators, the Series C Designators and the Series D Designator for the Preferred and Common Director must be ratified by the holders of a majority of the outstanding shares of Common Stock, which ratification may not be unreasonably withheld or delayed; provided further, however, no such ratification is required for any new Board Designee who has general experience with marketing and the travel related
e-commerce industry.

In the event of an initiation of removal of a Board Designee pursuant to Section 6(b)(i), the Holders shall vote all of the Stock of the Company now owned or hereafter acquired by them (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions to cause the removal from the Company’s Board of Directors of the Board Designee or Designees so designated for removal by the appropriate Designator or Designators; provided, however, in no event shall any party vote to remove any Board Designee unless the appropriate Designator or Designators have so directed pursuant to Section 6(b)(i). In the event of designation of a Board Designee pursuant to Section 6(b)(i), the Holders shall vote all of the Stock of the Company now owned or hereafter acquired by them (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions to cause the election to the Company’s Board of Directors of any new Board Designee or Designees so designated for election to the Company’s Board of Directors pursuant to Section 6(b)(ii).

Without the consent of the Requisite Investors, the Holders hereby agree that they will not take any action, by vote or otherwise, to increase the authorized number of directors constituting the Company’s Board of Directors to more than eight (8) directors, unless the holders of Convertible Preferred Stock are then entitled to elect, in addition to the two (2) Series A Directors described in Section 6(a)(iii) above and one Series C Director described in Section 6(a)(iv) above, two additional Series A Directors and one additional Series C Director pursuant to Article 4B, subparagraph 6C of the Certificate of Incorporation (the “Additional Directors”), in which case

Page 3 of 18

the Company’s Board of Directors shall consist of no more than eleven (11) members. If and for so long as the holders of Convertible Preferred Stock are entitled to elect the Additional Directors pursuant to Article 4B, subparagraph 6C of the Certificate of Incorporation, the Holders agree to vote all of the Stock of the Company now owned or hereafter acquired in favor of the election to the Board of Directors of two (2) persons designated from time to time by the Series A Designators and one (1) person designated from time to time by the Series C Designators.”

2. Counterparts. This Amendment may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

3. Governing Law. This Amendment shall be construed and enforced in accordance with and governed by the laws of the General Corporation Law of the State of Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to its principles of conflicts of laws.

[signature pages follow]

Page 4 of 18

IN WITNESS WHEREOF, the undersigned have executed this Amendment No. 1 to the Stockholders’ Agreement as a sealed instrument as of the day and year first above written.

COMPANY: KAYAK SOFTWARE CORPORATION
By:	/s/ Steve Hafner
Name:	Steve Hafner
Title:	CEO

[The remainder of this page is intentionally left blank.]

Page 5 of 18

INVESTORS:
GENERAL CATALYST GROUP II, L.P.		GENERAL CATALYST GROUP III, L.P.
By: General Catalyst Partners II, L.P. Its General Partner		By: General Catalyst Partners III, L.P. Its General Partner
By: General Catalyst GP II, LLC Its General Partner		By: General Catalyst GP III, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald Title: Member and Chief Financial Officer		Name: William J. Fitzgerald Title: Member and Chief Financial Officer
GC ENTREPRENEURS FUND II, L.P.		GC ENTREPRENEURS FUND III, L.P.
By: General Catalyst Partners II, L.P. Its General Partner		By: General Catalyst Partners III, L.P. Its General Partner
By: General Catalyst GP II, LLC Its General Partner		By: General Catalyst GP III, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald Title: Member and Chief Financial Officer		Name: William J. Fitzgerald Title: Member and Chief Financial Officer
GENERAL CATALYST GROUP V, L.P.		GC ENTREPRENEURS FUND V, L.P.
By: General Catalyst Partners V, L.P. Its General Partner		By: General Catalyst Partners V, L.P. Its General Partner
By: General Catalyst GP V, LLC Its General Partner		By: General Catalyst GP V, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald Title: Member and Chief Financial Officer		Name: William J. Fitzgerald Title: Member and Chief Financial Officer

Signature Page to Amendment No. 1 to Stockholders’ Agreement

GENERAL CATALYST GROUP V SUPPLEMENTAL, L.P.
By: General Catalyst Partners V, L.P. Its General Partner
By: General Catalyst GP V, LLC Its General Partner
By:	/s/ William J. Fitzgerald
Name: William J. Fitzgerald
Title: Member and Chief Financial Officer

Signature Page to Amendment No. 1 to Stockholders’ Agreement

/s/ Daniel Stephen Hafner

Daniel Stephen Hafner

Signature Page to Amendment No. 1 to Stockholders’ Agreement

/s/ Paul English

Paul English

Signature Page to Amendment No. 1 to Stockholders’ Agreement

ACCEL LONDON II L.P.
By:	Accel London II Associates L.P.
Its:	General Partner
By:	Accel London II Associates L.L.C.
Its:	General Partner
By:	/s/ Jonathan Biggs
	Name: Jonathan Biggs
	Title: Attorney in Fact
ACCEL LONDON INVESTORS 2006 L.P.
By:	Accel London II Associates L.LC.
Its:	General Partner
By:	/s/ Jonathan Biggs
	Name: Jonathan Biggs
	Title: Attorney in Fact

Signature Page to Amendment No. 1 to Stockholders’ Agreement

SEQUOIA CAPITAL XI SEQUOIA TECHNOLOGY PARTNERS XI SEQUOIA CAPITAL XI PRINCIPALS FUND By: SC XI Management, LLC A Delaware Limited Liability Company General Partner of Each
By:	/s/ Michael Moritz
Name:
Title:	Managing Member
SEQUOIA CAPITAL GROWTH FUND III SEQUOIA CAPITAL GROWTH PARTNERS III SEQUOIA CAPITAL GROWTH III PRINCIPALS FUND By: SCGF III Management, LLC A Delaware Limited Liability Company General Partner of Each
By:	/s/ Michael Moritz
Name:
Title:	Managing Member

Signature Page to Amendment No. 1 to Stockholders’ Agreement

EX-4.9

Exhibit 4.9

ELECTION AND AMENDMENT AGREEMENT

KAYAK SOFTWARE CORPORATION

KAYAK Software Corporation, a Delaware corporation (the “Corporation”), and the undersigned stockholders of the Corporation hereby enter into this Election and Amendment Agreement as of April 19, 2012 (the “Effective Date”).

Whereas, the undersigned stockholders include: (a) (i) the Requisite Holders, as such term is defined in the Corporation’s Amended and Restated Certificate of Incorporation, as amended (the “Certificate of Incorporation”), (ii) the holders of at least 66^2/3% of the Corporation’s Series D Convertible Preferred Stock; and (iii) Daniel Stephen Hafner and/or Paul English; (b) the Requisite Investors and each of the Designators, as such terms are defined in the Sixth Amended and Restated Stock Restriction and Co-Sale Agreement between the Corporation and the other parties thereto (the “Stock Restriction Agreement”); (c) the Requisite Investors and at least one Founder, as such terms are defined in the Sixth Amended and Restated Investor Rights Agreement, as amended, between the Corporation and the other parties thereto (the “Investor Rights Agreement”) and (d) the Requisite Investors, the Holders holding at least two-thirds of the Shares held by the Holders and each of the Designators, as such terms are defined in the Stockholders’ Agreement, dated as of May 6, 2010, as amended, between the Corporation and the other parties thereto (the “Stockholders Agreement”);

Whereas, the Corporation, a private corporation, is contemplating the consummation of a firm commitment underwritten initial public offering of Applicable Common Stock (as defined below) of the Corporation (the “IPO”);

Whereas, in connection with the consummation of the IPO the Corporation may recapitalize its existing Common Stock (as defined in the Certificate of Incorporation) into two new classes of common stock (the “Recapitalization”), namely a Class A Common Stock which shall be issued to the public (the Common Stock, or such Class A Common Stock as is issued in the IPO, as applicable at any time, the “Applicable Common Stock”) and a Class B Common Stock into which all existing capital stock of the Corporation shall be converted prior to the closing of the IPO (the “Class B Common Stock”);

Whereas, the election and agreements set forth herein are important to the IPO process and are otherwise to the mutual benefit of the Corporation and each of the undersigned stockholders;

Now, therefore, in consideration of the foregoing, the legal sufficiency of which is hereby acknowledged, the parties hereto hereby agree as follows:

1. Election to Convert Preferred Stock.

a. As used in this Election and Amendment Agreement, the following terms have the following respective meanings:

i. an “Applicable IPO” means an IPO consummated pursuant to a Registration Statement under the Securities Act of 1933, as amended, with an Effective

Time on or prior to December 31, 2012 and the consummation of which has been approved by the Board of Directors of the Corporation, or by any authorized Committee thereof;

ii. the “Closing” means the first sale of shares of Applicable Common Stock by the Corporation to the underwriters pursuant to an Applicable IPO; and

iii. the “Effective Time” means with respect to a Registration Statement, the time that the U.S. Securities and Exchange Commission declares such Registration Statement to be effective.

b. Pursuant to Section B.5O(1) of Article FOURTH of the Certificate of Incorporation, the undersigned stockholders hereby elect, such election to be effected immediately prior to but contingent upon the Closing, that all outstanding shares of Convertible Preferred Stock (as defined in the Certificate of Incorporation) shall automatically convert to shares of Common Stock or, if the Recapitalization has occurred, to shares of Class B Common Stock, in either case pursuant to the conversion procedures set forth in Section B.5O(2) of Article FOURTH of the Certificate of Incorporation as in effect at such time.

c. For purposes of clarity, (i) the foregoing election shall be deemed effected immediately prior to, but contingent upon, the Closing, without any further action by any party hereto, and may not be withdrawn, conditioned or otherwise modified except as provided in Section 11 hereof and (ii) references above to Section numbers in the Certificate of Incorporation will be deemed to be automatically and appropriately adjusted if and to the extent such Section numbers are modified by any amendment to the Certificate of Incorporation effected after the date hereof and prior to the Effective Time.

2. Amendment to the Stock Restriction Agreement. Pursuant to Section 14 of the Stock Restriction Agreement, Section 7 of the Stock Restriction Agreement is hereby amended to delete the phrase “of Common Stock in which” appearing therein, and to insert the following text in lieu thereof:

“of Common Stock (or other class of common stock of the Company) either (i) consummated pursuant to a Registration Statement under the Securities Act of 1933, as amended with an effective time on or prior to December 31, 2012 or (ii) in which”.

3. Amendments and Waiver Relating to the Investor Rights Agreement. Pursuant to Section 15(d) of the Investor Rights Agreement, the parties hereto hereby:

a. amend the Investor Rights Agreement to delete the definition of “Common Stock” appearing in Section 1 therein and to insert, in lieu thereof, the following: ““Common Stock” shall mean the Common Stock, $.001 par value, of the Company, as constituted as of the date of this Agreement; provided that if the Company has thereafter recapitalized and converted such Common Stock into a class of common stock, then “Common Stock” shall mean such class of common stock and/or any other class of common stock into which such class is convertible, as the context may require.”

b. amend the Investor Rights Agreement to delete the definition of “Qualified Public Offering” appearing in Section 1 therein and to insert, in lieu thereof, the following: ““Qualified Public Offering” shall mean a firm commitment underwritten public

2

offering of Common Stock which either (i) is consummated pursuant to a Registration Statement under the Securities Act of 1933, as amended with an effective time on or prior to December 31, 2012 or (ii) results in aggregate gross proceeds to the Company equal to or in excess of $25,000,000 with a price per share paid by the public for such shares equal to or in excess of $31.09 (such price subject to equitable adjustment in the event of any stock split, stock dividend, combination, reorganization, reclassification or other similar event occurring after March 22, 2010).”

c. waive the applicability of Section 12 of the Investor Rights Agreement to an Applicable IPO, to any of the securities issuances contemplated under Section 6 hereof, and to all other agreements and transactions contemplated in this Election and Amendment Agreement.

4. Amendment to the Stockholders Agreement. Pursuant to Section 18 of the Stockholders’ Agreement, Section 10 of the Stockholders’ Agreement is hereby amended to delete such Section in its entirety and to insert, in lieu thereof, the following:

“10. Termination. This Agreement, and the respective rights and obligations of the parties hereto, shall terminate upon the completion of a firm commitment underwritten public offering of Common Stock (or other class of common stock of the Company) which either (i) is consummated pursuant to a Registration Statement under the Securities Act of 1933, as amended with an effective time on or prior to December 31, 2012 or (ii) results in aggregate gross proceeds to the Company equal to or in excess of $25,000,000 with a price per share paid by the public for such shares equal or in excess of $31.09 per share (such price subject to equitable adjustment in the event of any stock split, stock dividend, combination, reorganization, reclassification or other similar event occurring after March 22, 2010) (a “Qualified Public Offering”); provided, however, that (x) Sections 1 through 3 shall terminate on the earlier of (i) the completion of a Qualified Public Offering and (ii) ten (10) years after the date hereof, (y) Section 8 shall terminate pursuant to the terms as set forth therein and (z) Section 9(a) shall terminate upon the completion of a firm commitment underwritten public offering of Common Stock by the Company.”

5. Amendment to Certificate of Incorporation. Each of the undersigned stockholders hereby consent, in accordance with Section 228 of the Delaware General Corporation Law, to the following actions by written consent and without a meeting, which actions and resolutions shall have the same force and effect as if duly adopted at a special meeting duly called and held at which a quorum was present and acting throughout:

a. That the Amendment to the Amended and Restated Certificate of Incorporation of the Corporation (the “Charter Amendment”), substantially in the form attached hereto as Exhibit A, be, and hereby is, approved;

b. That the appropriate officers of the Corporation be, and each of them acting singly hereby is, authorized to execute the Charter Amendment; and that, the Corporation is hereby authorized to file the Charter Amendment with the Secretary of State of the State of Delaware; and

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c. That at any time prior to the effectiveness of the filing of the Charter Amendment with the Secretary of State of the State of Delaware, notwithstanding authorization of the Charter Amendment by the stockholders of the Corporation, the Board of Directors of the Corporation, in its discretion, may abandon and not file such Charter Amendment without further action by the stockholders of the Corporation.

6. Additional Consideration to Certain Holders of Series D Convertible Preferred Stock.

a. In further consideration for the elections and agreements set forth herein by the Eligible Series D Holders (as defined below), the Corporation agrees to sell to each Eligible Series D Holder, upon such Eligible Series D Holder’s valid Election (as defined below), such number of shares of Applicable Common Stock as is determined pursuant to the further provisions of this Section 6; provided that each of the following holders of Series D Convertible Preferred Stock hereby acknowledge and agree that, notwithstanding their execution of this Election and Amendment Agreement on or prior to May 3, 2012, they shall not be deemed Eligible Series D Holders solely for the purposes of this Section 6.a and the following Section 6.b, and accordingly shall not be eligible to make an Election nor to purchase any Election Shares:

Accel London II L.P.

Accel London Investors 2006 L.P.

GC Entrepreneurs Fund II, L.P.

GC Entrepreneurs Fund III, L.P.

GC Entrepreneurs Fund V, LP

General Catalyst Group II, L.P.

General Catalyst Group III, L.P.

General Catalyst Group V Supplemental, LP

General Catalyst Group V, LP

Sequoia Capital Growth Fund III

Sequoia Capital Growth III Principals Fund

Sequoia Capital Growth Partners III

b. An “Election” may be made by an Eligible Series D Holder solely upon the terms and conditions set forth in this Section 6.b: such Eligible Series D Holder must deliver to the Corporation during the Election Period a written notice specifying that such Eligible Series D Holder elects to purchase from the Corporation either all of such Eligible Series D Holder’s Election Shares or such lesser number of whole Election Shares as is specified therein by such Eligible Series D Holder and, within seven (7) Business Days of the Closing, the payment of the Per Share

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Price multiplied by the number of Election Shares specified in such written notice, by wire transfer of immediately available funds pursuant to the wiring instructions of the Corporation attached hereto as Exhibit B. A written Election notice must be delivered by one of the following methods, and will be deemed delivered solely upon receipt thereof by the Corporation: (a) by-hand delivery to the Chief Financial Officer of the Corporation (b) by a recognized overnight courier service, with certification of receipt requested, to the Chief Financial Officer of the Corporation at KAYAK Software Corporation, 55 North Water Street, Suite 1, Norwalk CT 06854 or (c) by email to each of mreiter@kayak.com and kklein@kayak.com. The closing of the purchase of Election Shares by an Eligible Series D Holder pursuant to a properly made Election shall occur upon timely receipt of the purchase price by the Corporation and, upon receipt of such payment, the Corporation shall issue to such Eligible Series D Holder the Election Shares paid for as evidenced by a stock certificate, with appropriate legends, promptly after such closing. The Corporation hereby expressly confirms, represents and warrants that the elections and agreements set forth herein by the Eligible Series D Holders and the further cash consideration specified above collectively constitute due and valid consideration in respect of any such issuance of Election Shares, and that each such share of Applicable Common Stock shall, upon issuance, be validly issued, fully paid and non-assessable.

c. In the event of a Closing of an Applicable IPO in which the Per Share Price is less than $27.00 (such price subject to equitable adjustment in the event of any stock split, stock dividend, combination, reorganization, reclassification or other similar event occurring after the date hereof), then in further consideration for the elections and agreements set forth herein by the Eligible Series D Holders, and without the requirement of any cash payment or any further action by the Eligible Series D Holders, the Corporation agrees to issue to each Eligible Series D Holder (including any Eligible Series D Holder listed in 6.a), within five (5) Business Days after the Closing, the number of True-Up Shares applicable to such Eligible Series D Holder as evidenced by a stock certificate with appropriate legends. The Corporation hereby expressly confirms, represents and warrants that the foregoing specified consideration constitutes due and valid consideration in respect of any such issuance of True-Up Shares, and that each such share of Applicable Common Stock shall, upon issuance, be validly issued, fully paid and non-assessable.

d. It is expressly understood and agreed that: (i) an Election may only be made during the Election Period, if any; (ii) an Election Period may never occur; and (iii) the Corporation makes no representation or covenant that an Applicable IPO will be consummated.

e. The Corporation shall, not later than two calendar days after the Closing of an Applicable IPO in which the Per Share Price is less than $31.09 (such price subject to equitable adjustment in the event of any stock split, stock dividend, combination, reorganization, reclassification or other similar event occurring after the date hereof), provide by written notice to each Eligible Series D Holder a copy of the final Exhibit C hereto, reflecting any exercise of the Series D Convertible Preferred Stock warrant held by Gold Hill Venture Lending 03, L.P. Such written

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notice shall be provided to each Eligible Series D Holder by email to the address specified by such Eligible Series D Holder on Exhibit C hereto at the time of such stockholder’s execution hereof; provided that if any Eligible Series D Holder does not provide an email address pursuant to this sentence, the Corporation shall provide such notice to such stockholder by US Mail at the address for such stockholder set forth in the Series D Convertible Preferred Stock Purchase Agreement dated December 20, 2007.

f. As used in this Section 6, the following terms have the following meanings:

i. “Business Day” means any day on which national banking institutions in the State of New York are open to the public for conducting business and are not required to close.

ii. “Election Period” means the period, if any, commencing the day of the Closing in which the Corporation and the underwriters establish a final Per Share Price which is less than $31.09, and ending at 5:00 p.m., East Coast time, on the fifth Business Day following such date. Upon request at or after any such Closing, the Corporation will confirm the date of such Closing and the date upon which the Election Period expires.

iii. “Election Shares” means, with respect to any Eligible Series D Holder, a number of shares of Applicable Common Stock calculated as follows: (i) dividing Twenty Million Dollars ($20,000,000) by the Per Share Price, and then (ii) multiplying the number determined in clause (i) by a fraction, the numerator of which is the number of outstanding shares of Series D Convertible Preferred Stock registered in the name of such Eligible Series D Holder at the close of business on May 3, 2012, and the denominator of which is the total number of shares of Series D Convertible Preferred Stock outstanding at the close of business on May 3, 2012, and finally (iii) rounding the aggregate number determined in clause (ii) up or down, as applicable, to the nearest whole number of shares;

iv. “Eligible Series D Holder” means each holder of Series D Convertible Preferred Stock of the Corporation that has executed and delivered to the Corporation this Election and Amendment Agreement on or prior to May 3, 2012.

v. “Per Share Price” means the final price per share to the public in the Applicable IPO.

vi. “True-Up Shares” means, with respect to any Eligible Series D Holder a number of shares of Applicable Common Stock calculated as follows: (i) determining the amount, if any, by which $27.00 (such price subject to equitable adjustment in the event of any stock split, stock dividend, combination, reorganization, reclassification or other similar event occurring after the date hereof) exceeds the Per Share Price and then (ii) dividing such excess amount determined in clause (i) by the Per Share Price, and then (iii) multiplying the amount determined in clause (ii) by the number of outstanding shares of Series D Convertible Preferred Stock registered in the name of such Eligible Series D Holder at the close of business on May 3, 2012 and finally (iv) rounding the aggregate number determined in clause (iii) up or down, as applicable, to the nearest whole number of shares.

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7. Certain Representations and Warranties by the Stockholders. Each of the undersigned stockholders, severally and not jointly, represents and warrants that:

a. If such stockholder is an Eligible Series D Holder, then (i) it is an “accredited investor” within the meaning of Rule 501 under the Securities Act of 1933, as amended (the “Securities Act”); (ii) it will acquire the Applicable Common Stock to be acquired by it hereunder for its own account and that such stock is being and will be acquired by it for the purpose of investment and not with a view to distribution or resale thereof; (iii) it understands and agrees that, until registered under the Securities Act or transferred pursuant to the provisions of Rule 144 under the Securities Act, all certificates evidencing any of the Applicable Common Stock purchased hereunder shall bear a legend, prominently stamped or printed thereon, to the effect that such securities may not be sold other than pursuant to a registered offering or an applicable registration exemption under the Securities Act; and (iv) at the time of execution hereof and through the close of business on May 3, 2012, such Eligible Series D Holder is the owner of the number of shares of Series D Convertible Preferred Stock set forth opposite such stockholder’s name on Exhibit C hereto;

b. The execution, delivery and performance by such stockholder of this Election and Amendment Agreement has been duly authorized by all requisite corporate, limited liability, partnership or other action, as applicable, of such stockholder. Such stockholder has duly authorized, executed and delivered this Election and Amendment Agreement and this Election and Amendment Agreement constitutes the valid and binding obligation of such stockholder enforceable in accordance with its terms; and

c. None of (i) the execution and delivery of this Election and Amendment Agreement, (ii) the consummation of the transactions, elections and consents contemplated by this Election and Amendment Agreement, nor (iii) the purchase (or receipt) of Applicable Common Stock hereunder by such stockholder, has constituted or resulted in or will constitute or result in (A) a default under or violation of any term or provision of any agreement or arrangement to which such stockholder is a party or by which such stockholder is bound, (B) a default under or violation of such stockholder’s organizational and/or operating documents or (C) violate any applicable law, statute, rules or regulations.

8. Certain Representations and Warranties by the Corporation. The Corporation represents and warrants that:

a. The execution, delivery and performance by the Corporation of this Election and Amendment Agreement has been duly authorized by all requisite corporate action of the Company, including any required stockholder approval. The Corporation has duly authorized, executed and delivered this Election and Amendment Agreement and this Election and Amendment Agreement constitutes the valid and binding obligation of the Corporation enforceable in accordance with its terms; and

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b. Subject to the accuracy of the representations and warranties set forth in Section 7.a, none of (i) the execution and delivery of this Election and Amendment Agreement, (ii) the consummation of the transactions contemplated by this Election and Amendment Agreement, nor (iii) the purchase (or receipt) of Applicable Common Stock hereunder by an Eligible Series D Holder, has constituted or resulted in or will constitute or result in (A) a default under or violation of any term or provision of any agreement or arrangement to which the Corporation is a party or by which the Corporation is bound, (B) a default under or violation of the Corporation’s Certificate of Incorporation or By-laws or (C) violate any applicable law, statute, rules or regulations.

9. Lock-Up Acknowledgement. Each Eligible Series D Holder hereby affirms and agrees that any shares of Applicable Common Stock that it purchases and/or receives hereunder are bound by the restrictions set forth in the Lock-Up Letter agreement executed by such Eligible Series D Holder in favor of Morgan Stanley & Co. Incorporated and Deutsche Bank Securities Inc.

10. Counterparts. This Election and Amendment Agreement may be executed in counterparts. For purposes of clarity, it is understood and agreed that (i) one or more stockholders listed on the signature pages hereof may not execute this Election and Amendment Agreement and (ii) notwithstanding the foregoing, this Election and Amendment Agreement shall be effective as to each signatory hereto upon such signatory’s execution hereof.

11. Amendments, Waivers, etc. No provision of this Election and Amendment Agreement may be amended, waived, terminated, withdrawn or otherwise modified except pursuant to, and any provision of this Election and Amendment Agreement may be amended, waived, terminated, withdrawn or otherwise modified solely by, a written consent executed by the (i) Corporation, (ii) holders of at least 66^2/3% of the Corporation’s Series D Convertible Preferred Stock and (iii) the Requisite Investors; provided that the Corporation may update Exhibit C to reflect any exercise of the Series D Convertible Preferred Stock warrant held by Gold Hill Venture Lending 03, L.P. The Corporation may not assign any of its rights or obligations hereunder without the prior written consent of (i) holders of at least 80% of the Corporation’s Series D Convertible Preferred Stock and (ii) the Requisite Investors; none of the undersigned stockholders may assign any of its rights or obligations hereunder without the prior written consent of the Corporation.

12. Governing Law. This Election and Amendment Agreement shall be construed and enforced in accordance with and governed by the laws of the General Corporation Law of the State of Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to its principles of conflicts of laws.

13. Expenses. Each party shall bear its own expenses and legal fees in connection with the execution of this Election and Amendment Agreement. If any action at law or in equity is necessary to enforce or interpret the terms of this Election and Amendment Agreement, the prevailing party shall be entitled to reasonable attorneys’ fees, costs and disbursements in addition to any other relief to which such party may be entitled.

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14. Survival. All representations and warranties made as set forth in this Election and Amendment Agreement shall survive the execution of this Election and Amendment Agreement and the consummation of the transactions contemplated herein.

In witness whereof, the Corporation and the undersigned stockholders have executed this Election and Amendment Agreement as of the date first written above.

[signature pages follow]

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CORPORATION:
KAYAK SOFTWARE CORPORATION
By:	/s/ Daniel Stephen Hafner
Name:	Daniel Stephen Hafner
Title:	President

[The remainder of this page is intentionally left blank]

STOCKHOLDERS:

/s/ Daniel Stephen Hafner
Daniel Stephen Hafner	Paul English

ACCEL LONDON II L.P.		ACCEL LONDON INVESTORS 2006 L.P.
By: Accel London II Associates L.P.		By: Accel London II Associates L.L.C.
Its General Partner		Its General Partner
By: Accel London II Associates L.L.C.
Its General Partner
By:	/s/ Jonathan Biggs	By:	/s/ Jonathan Biggs
Name:	Jonathan Biggs	Name:	Jonathan Biggs
Title:	Attorney in Fact	Title:	Attorney in Fact

GENERAL CATALYST GROUP II, L.P.		GENERAL CATALYST GROUP III, L.P.
By: General Catalyst Partners II, L.P. Its General Partner		By: General Catalyst Partners III, L.P. Its General Partner
By: General Catalyst GP II, LLC Its General Partner		By: General Catalyst GP III, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald	Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer	Title:	Member and Chief Financial Officer
GC ENTREPRENEURS FUND II, L.P.		GC ENTREPRENEURS FUND III, L.P.
By: General Catalyst Partners II, L.P. Its General Partner		By: General Catalyst Partners III, L.P. Its General Partner
By: General Catalyst GP II, LLC Its General Partner		By: General Catalyst GP III, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald	Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer	Title:	Member and Chief Financial Officer
GENERAL CATALYST GROUP V, L.P.		GC ENTREPRENEURS FUND V, L.P.
By: General Catalyst Partners V, L.P. Its General Partner		By: General Catalyst Partners V, L.P. Its General Partner
By: General Catalyst GP V, LLC Its General Partner		By: General Catalyst GP V, LLC Its General Partner
By:	/s/ William J. Fitzgerald	By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald	Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer	Title:	Member and Chief Financial Officer

GENERAL CATALYST GROUP V SUPPLEMENTAL, L.P.
By: General Catalyst Partners V, L.P. Its General Partner
By: General Catalyst GP V, LLC Its General Partner
By:	/s/ William J. Fitzgerald
Name:	William J. Fitzgerald
Title:	Member and Chief Financial Officer

SEQUOIA CAPITAL XI

SEQUOIA TECHNOLOGY PARTNERS XI

SEQUOIA CAPITAL XI PRINCIPALS FUND

By: SC XI Management, LLC A Delaware Limited Liability Company General Partner of Each
By:	/s/ Michael Moritz
Name:	Michael Moritz
Title:	Managing Member

SEQUOIA CAPITAL GROWTH FUND III

SEQUOIA CAPITAL GROWTH PARTNERS III

SEQUOIA CAPITAL GROWTH III PRINCIPALS FUND

By:	SCGF III Management, LLC
	A Delaware Limited Liability Company
	General Partner of Each
By:	/s/ Michael Moritz
Name:	Michael Moritz
Title:	Managing Member

TRIDENT CAPITAL FUND-V, L.P

TRIDENT CAPITAL FUND-V AFFILIATES FUND, L.P.

TRIDENT CAPITAL FUND-V AFFILIATES FUND (Q), L.P.

TRIDENT CAPITAL FUND-V PRINCIPALS FUND, L.P.

TRIDENT CAPITAL PARALLEL FUND-V, C.V.

Executed on behalf of the foregoing funds

by the undersigned, as an authorized signatory

of the respective general partner of each such fund:

    (signature)

    (print name)

NORWEST VENTURE PARTNERS VII-A, LP	NORWEST VENTURE PARTNERS X, LP
By: Itasca VC Partners VII-A, LLC	By: Genesis VC Partners X, LLC
Its General Partner	Its General Partner
By:	By:
Name:	Name:
Title:	Title:

OAK INVESTMENT PARTNERS XII, LIMITED PARTNERSHIP

By: Oak Associates XII, LLC, its General Partner
By:	/s/ Iftikar A. Ahmed
Name:	Iftikar A. Ahmed
Title:	Managing Member

TENAYA CAPITAL V, L.P.
By:	Tenaya Capital V GP, L.P., its General Partner
By:	Tenaya Capital V GP, LLC, its General Partner
By:
Name:
Title:
TENAYA CAPITAL V-P, L.P.
By:	Tenaya Capital V GP, L.P., its General Partner
By:	Tenaya Capital V GP, LLC, its General Partner
By:
Name:
Title:
TENAYA CAPITAL B, LP
By:
By:
By:
Name:
Title:

GOLD HILL VENTURE LENDING 03, L.P.

By:

Name:

Title:

Matthias Zahn

Wolfgang Heigl

Andreas Stegmann

Pierre Jacoby-Schrade

Christian Saller

Exhibit A

Charter Amendment

EIGHTH AMENDMENT TO

AMENDED AND RESTATED

CERTIFICATE OF INCORPORATION

OF

KAYAK SOFTWARE CORPORATION

(Pursuant to Sections 242 of the

General Corporation Law of the State of Delaware)

KAYAK Software Corporation, a corporation organized and existing under and by virtue of the provisions of the General Corporation Law of the State of Delaware (the “Corporation”),

DOES HEREBY CERTIFY:

1) That the name of this corporation is KAYAK Software Corporation, and that this corporation was originally incorporated pursuant to the General Corporation Law of the State of Delaware (the “DGCL”) on January 14, 2004 under the name Travel Search Company, Inc.;

2) That the Board of Directors duly adopted resolutions proposing to amend the Amended and Restated Certificate of Incorporation of this corporation, declaring said amendment to be advisable and in the best interests of this corporation and its stockholders, and authorizing the appropriate officers of this corporation to solicit the consent of the stockholders therefor;

3) That the Board of Directors of the Corporation directed that such amendment be submitted to the stockholders of the Corporation for their consent and approval and, in lieu of a meeting and vote of stockholders, the stockholders have given written consent to said amendment in accordance with the provisions of Section 228 of the DGCL.

4) That said amendment was duly adopted in accordance with the provisions of Sections 242 and 228 of the DGCL; which resolutions and consent setting forth the proposed amendment and restatement is as follows:

RESOLVED, that the Amended and Restated Certificate of Incorporation of this Corporation, as amended, be further amended to delete the word “and” appearing immediately

before clause (ix) in subparagraph B.5E of Article FOURTH and to insert the following new clause (x) in such subparagraph B.5E of Article FOURTH:

“; and (x) shares of Common Stock issued, or deemed issued, pursuant to (A) a firm commitment underwritten public offering consummated pursuant to a Registration Statement under the Securities Act of 1933, as amended, with an effective time on or prior to December 31, 2012 and/or (B) pursuant to the terms of that certain Election and Amendment Agreement, dated on or about April 19, 2012, by and between the Corporation and the other parties thereto”.

[The remainder of this page is intentionally left blank. Signature page follows.]

IN WITNESS WHEREOF this Eighth Amendment to Amended and Restated Certificate of Incorporation has been executed by the undersigned this 18^th day of April, 2012.

KAYAK SOFTWARE CORPORATION
Name:	Daniel Stephen Hafner
Title:	Chief Executive Officer

Exhibit B

Wire Instructions

Remit payment by wire as follows:

Silicon Valley Bank

3003 Tasman Drive

Santa Clara, CA 95054

Routing & Transit #:

Swift Code:

Beneficiary: Kayak Software Corporation

Beneficiary Account #:

Exhibit C

Holders of Series D Convertible Preferred Stock

HOLDER	Series D Shares			Email address (optional)
Accel London II L.P.		472,567
Accel London Investors 2006 L.P.		9,890
GC Entrepreneurs Fund II, L.P.		8,770
GC Entrepreneurs Fund III, L.P.		8,423
GC Entrepreneurs Fund V, LP		29,594
General Catalyst Group II, L.P.		232,461
General Catalyst Group III, L.P.		232,808
General Catalyst Group V Supplemental, LP		945,196
General Catalyst Group V, LP		472,598
Gold Hill Venture Lending 03, L.P.		48,246	*
Norwest Venture Partners VII-A, LP		120,615
Norwest Venture Partners X, LP		120,615
Oak Investment Partners XII, Limited Partnership		2,171,058
Sequoia Capital Growth Fund III		1,816,181
Sequoia Capital Growth III Principals Fund		93,790
Sequoia Capital Growth Partners III		19,877
Tenaya Capital B, LP		241,231
Tenaya Capital V, LP		567,163
Tenaya Capital V-P, LP		156,531
Trident Capital Fund-V Affiliates Fund (Q), L.P.		1,199

Trident Capital Fund-V Affiliates Fund, L.P.	1,256
Trident Capital Fund-V Principals Fund, L.P.	6,255
Trident Capital Fund-V, L.P.	216,100
Trident Capital Parallel Fund-V, C.V.	16,418

* Subject to increase to up to 110,246 shares in total, if and to the extent an outstanding warrant to purchase 62,000 shares of Series D Convertible Preferred Stock is exercised.

EX-10.66

Exhibit 10.66

CONFIDENTIAL TREATMENT

AMADEUS PRODUCTS AND SERVICES AGREEMENT

This Products and Services Agreement (“Agreement”) is effective as of 1^st day of January, 2012 (“Effective Date”) and is made between:

Amadeus IT Group, S.A., a Spanish company with principal offices at Salvador de Madariaga, 1—28027 Madrid, Spain (“Amadeus”) including its group entities, and

KAYAK Software Corporation, a Delaware, U.S.A. corporation with principal offices at 55 North Water Street, Suite 1, Norwalk, CT 06854 USA (“Kayak” or “Subscriber”);

(each a “Party” and collectively the “Parties”).

RECITALS

WHEREAS, Amadeus has developed and is operating a fully automated global reservations and distribution system (the “Amadeus System”), with the ability to perform comprehensive information, communications, and related functions; and

WHEREAS, Subscriber wishes to access and use the Amadeus System and other related products and services, solely for the purposes set forth in this Agreement;

IT IS AGREED:

1. DEFINITIONS

The following definitions shall apply to the terms used in this Agreement:

1.1 “Affiliates” means in respect of a Party, an entity in which a party owns more than fifty percent of the voting rights.

1.2 “Agreement” means this Products and Services Agreement, and any Exhibit attached hereto, as amended or supplemented from time to time.

1.3 “Amadeus Data” means all information, results, or data provided by Amadeus in the course of Subscriber’s use of the Software and/or access to the Amadeus System.

1.4 “Amadeus Group” means the group of legal entities founded to organize, develop, operate and distribute the Amadeus System.

1.5 “Amadeus System” or “System” means the advanced computer reservation system for the travel industry developed, owned, operated and/or distributed by Amadeus.

1.6 “Amadeus Web Services” means the Amadeus web services interface and related infrastructure, including but not limited to hardware, software and services, made available by the Amadeus Group to Subscriber for the development of certain applications as referenced in Attachment B hereto.

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* CONFIDENTIAL TREATMENT REQUESTED. OMITTED PORTIONS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES ACT OF 1933, AS AMENDED.

1.7 “Non-Air Booking” means an individual car or hotel reservation entry, or entries, in the itinerary portion of a PNR processed / booked in the Amadeus System which has not been cancelled, unconfirmed or unfulfilled.

1.8 “[            ]*” means the process by which search data for [            ]* MetaPricer Queries is [            ]* sent by Amadeus to Subscriber at [            ]*.

1.9 “Content” means provider data available to Subscriber in the Amadeus System.

1.10 “Customer Equipment” means equipment, hardware, software and any other material that is not provided by Amadeus.

1.11 “Internet User” means an individual that accesses Amadeus System at the Subscriber Sites.

1.12 “MetaPricer” means a tool that enables searching, selecting or sorting for low fare air travel options that include (i) one-way, round trip and multiple segment trips, (ii) with travel ranging from multiple hours to multiple days, (iii) involving departure and/or arrival at single or multiple airports, and (iv) including all passenger types, as well as up to 9 passengers. Any reference to MetaPricer includes MasterPricer.

1.13 “MetaPricer Query” means a Search submitted to MetaPricer for information including air carriers, lowest fares, and fare availability between two or more cities or airports. MetaPricer Query will exclude: (i) test queries performed in a testing environment, (ii) queries posed to MetaPricer by Amadeus in connection with its monitoring of the MetaPricer usage, and (iii) queries that return no Content or result in error messages that are not attributable to a Search for which there are no viable results.

1.14 “North America Domestic Query” means a MetaPricer Query with travel origin located within the United States or Canada and the destination located in the United States or Canada.

1.15 “PNR” means passenger name record.

1.16 “Provider” means a provider of travel related services that makes its data available through the Amadeus System.

1.17 “Search” means a request from an Internet User to Subscriber for information about airfare, hotels or rental car rates.

1.18 “Software” means software and related documentation provided by Amadeus to Subscriber under this Agreement, including MetaPricer, [            ]*, and Amadeus Web Services.

1.19 “Split-Query” means a Search for which Subscriber submits more than one MetaPricer Query; provided that if more than 30% of Split Queries specify more than one carrier, then the parties will discuss in good faith a revision of this definition. For the avoidance of doubt, each MetaPricer Query in a Split Query must have

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* CONFIDENTIAL TREATMENT REQUESTED. OMITTED PORTIONS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 406 PROMULGATED UNDER THE SECURITIES ACT OF 1933, AS AMENDED.

substantially similar search parameters as those supplied by the Internet User for the underlying Search.

1.20 “Subscriber Sites” means the website Kayak.com and all of the websites and mobile applications owned, operated or powered by Subscriber.

1.21 “Supplier Direct Partners” means specific hotel suppliers with whom Subscriber has direct distribution agreements.

1.22 “ Transaction” or “Central System Transaction” means a request to process data that is transmitted to the Amadeus System. Multiple data elements transmitted to the Amadeus System in a string will be counted as one Transaction. Data elements transmitted via wizards, macros, robotics and similar means may result in multiple Transactions that are not apparent to the Amadeus System user. However, reporting or other data consolidation seeking commands from Amadeus system will not be counted as transactions.

1.23 “Web Services Message” means a grammar describing a dialogue in XML format (request/ response) that can be used to interact with the Amadeus Platform.

1.24 “Year” means each successive twelve month period from the Effective Date.

2. TERM

This Agreement shall be effective from 1^st of January 2012 for a period of five (5) years (the “Initial Term”), and will thereafter automatically renew for six (6) month periods (“Renewal Term(s)”) unless terminated by either Party with thirty (30) days written notice prior to the expiration of the Initial Term or any Renewal Term.

3. PRODUCTS AND SERVICES

3.1 License

Amadeus hereby grants to Subscriber, subject to the terms and conditions stated herein, a limited, non-transferable and non-exclusive right to use, perform and display the Software.

3.2 Products

3.2.1 MetaPricer

For each MetaPricer Query submitted, Amadeus will endeavour to return as many low fare air travel information results as possible; provided that Subscriber acknowledges that the maximum number of itineraries returned in response to a particular MetaPricer Query shall be [            ]* and the maximum number of airlines listed in such results shall be [            ]* airlines. This information will include airline code, departure time, airport code, arrival time, code share information, equipment type, fare availability, flight duration, base prices, applicable taxes and fees, and any other information required by law to be displayed to users or mutually agreed to between the Parties.

The list of itineraries and fares returned by MetaPricer will be computed by Amadeus in order to return the itineraries that are identical to the itineraries returned individually

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by the Internet web site of each Amadeus System Provider, subject to Subscriber having an agreement in place with the Provider as necessary. Amadeus will monitor the accuracy of the data returned by MetaPricer Queries and Subscriber shall have the right to use such data to benchmark Amadeus’s accuracy against competitors and Provider websites.

At a regular interval period of time, Amadeus and Subscriber will meet to review and assess the quality of the data provided and discuss potential improvements.

For each six month period of the Agreement beginning with the Effective Date, Amadeus shall allow Subscriber to conduct a number of queries per second based on the volume projections provided by Subscriber at the beginning of each such f six (6) month period. Subscriber’s access will be limited to the numbers that it has provided. However, if Subscriber determines that it needs or wants a higher query per second ratio, it can submit a revised projection to Amadeus. Amadeus agrees to accommodate any such revised projection unless it can demonstrate to Subscriber that a higher query per second ratio would result in a greater than [            ]* increase in volume, in which case the parties will agree in good faith upon a timeframe within which to accommodate the increase in volume.

3.2.2 [            ]*

[            ]*

During these [            ]*, Subscriber will be authorised to perform up to [            ]* MetaPricer Queries (which may be performed as Split Queries) per month. Amadeus may restrict the times during the day at which Subscriber can send these Queries: for example peak hour of traffic might be excluded; provided, however, that such restrictions shall not exceed three consecutive hours at any time and in aggregate shall not exceed 5 hours in any 24 hour period.

3.2.3 Amadeus Web Services

Amadeus Web Services will be provided pursuant to the terms of the Amadeus Web Services agreement included herein as Attachment B.

It will be Subscriber’s responsibility to create, support and maintain the Graphical User Interface (“GUI”), which uses the Amadeus Data provided.

3.3 Services

3.3.1 Maintenance and Enhancements

Software maintenance is included as part of the MetaPricer fee, without additional charge. MetaPricer [            ]* will include such enhancements and updates, including industry changes, as Amadeus shall, at no additional charge, make generally available to other customers of MetaPricer [            ]*, respectively.

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3.3.2 Service Levels

Amadeus shall provide the services in accordance with the service levels to be agreed and set out in Attachment C to this Agreement.

3.3.3 Additional Services

Subscriber may request and Amadeus may agree, but by no means would be obliged, to perform additional services relating to MetaPricer [            ]* outside the scope of Amadeus’s obligations under this Agreement, including but not limited to development and operations support required by Subscriber to develop or customize to Subscriber’s requirements. The provision of such services shall be governed by a Statement of Work (“SOW”) agreed to by both Parties. Subscriber shall pay Amadeus the fees (based on Amadeus’ standard rates, as charged to its customers generally) set forth in the applicable SOW.

4. SYSTEM ACCESS

4.1 General

Amadeus will grant access to the Amadeus System via a separate Amadeus Web Services Agreement included herein as Attachment B. Subscriber will use its own or a third party software interface to connect to Amadeus System and will be solely responsible for the integration of the interface.

4.2 System Modifications

Amadeus may in its discretion modify, substitute and/or upgrade or enhance the functions and components of, and data provided through, the Amadeus System; provided that each such modification, substitution, upgrade or enhancement shall not result in any reduction in functionality or data as compared to that available to Subscriber prior to such release, Amadeus will provide all necessary support to enable Subscriber to implement such release, and that there will be no additional charge Subscriber.

4.3 Scheduled Downtime

Amadeus may schedule System and Amadeus Web Services downtime for maintenance after giving prior written notice of at least 72 hours. Amadeus shall use its reasonable commercial efforts to ensure that the occurrence and duration of any such periods of downtime shall be minimized.

4.4 Suspension of Access

AMADEUS may suspend access to the Amadeus System without liability if:

(1) Amadeus reasonably believes that an abuse or misuse of the Amadeus System is being caused, permitted or enabled by Subscriber or on Subscriber’s behalf; or

(2) Subscriber attempts unauthorized modifications to the System; or

(3) Subscriber fails to pay Amadeus any Charges under this Agreement for more than ninety (90) days after payment is due.

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In all cases where Amadeus takes any action to suspend access above it will use best efforts to first provide ten (10) days prior notice to Subscriber so that the System abuse/misuse or unauthorized use may be cured prior to any suspension. If Amadeus suspends access pursuant to this provision, then: (i) it will use best efforts to restore Subscriber’s access immediately upon correction of the problem, and (ii) Subscriber shall not be liable for minimum fees for the period of the suspension.

4.5 Use Restrictions

Subscriber shall take reasonable precautions to prevent unauthorized access to the Amadeus System. Further, Subscriber agrees not to use the Amadeus System for:

(1) Reservation of space in anticipation of demand;

(2) Improper creation or modification of records;

(3) Disclosure of the systems to persons other than Subscriber employees; except for contractors or other third parties engaged by Subscriber;

(4) Caching of data that is not expressly authorized by Amadeus.

(5) Access via third party products (e.g. robotic tools) that are not expressly authorized and certified by Amadeus

4.6 Transaction Counts

Amadeus shall provide Subscriber with detailed Transaction reports, including detailed break-down and usage with respect to the preceding month by the 20^th of each calendar month. Subscriber will have the right to request any additional records upon which the Transactions were based. If Subscriber does not raise any objections with the reports within fifteen (15) business days, then Subscriber shall pay the Transaction Fees as set forth on Exhibit A, based on the reports and invoices provided by Amadeus. In the event Subscriber determines that the Transaction reports differ by more than 5% from Subscriber’s own data, Subscriber shall notify Amadeus and the parties will defer resolution to the Quarterly Status Meeting (as defined in Section 15.12).

5. SCOPE OF USE

5.1 General

Subscriber agrees to use the Amadeus System and the Software solely as follows

(a) only for informational purposes to search, select and sort low fare air travel options.

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(b) for searching, selecting and sorting for non-air travel options, as well as to facilitate Non-Air Bookings by allowing Internet Users to complete transactions directly with Providers without leaving a Subscriber Site.

5.2 Provider Agreements

Amadeus will include airlines’ airfares in MetaPricer provided that if any particular airline or travel agency requires Subscriber to have its own direct agreement with airline or travel agency in order to access the airline’s fares through the Amadeus System, then access will be provided to that airline’s fares only if Subscriber enters into such a direct agreement. Amadeus agrees to use commercially reasonable efforts to assist Subscriber in obtaining direct agreements. Amadeus will include search data from all Subscriber partners (airline or travel agency) [            ]* unless a particular partner requests that its data not be included [            ]*, in which case Amadeus will notify Subscriber that particular partner has made such a request.

Amadeus will not be liable for the accuracy of Content available in the Amadeus System provided that any such inaccuracy is caused by the Provider and not by Amadeus.

5.3 Use of Data

Subscriber may use the Amadeus Data that it obtains under this Agreement only for the purpose of providing Subscriber’s services via the Subscriber Sites, including Subscriber powered co-branded and affiliated sites (the “Authorized Use”). Amadeus acknowledges and agrees that Subscriber’s services shall include facilitated booking functionality pursuant to which an Internet User may complete a Non-Air Booking or an air fare booking directly with a Provider without leaving the Subscriber Sites.

Amadeus Data may not be published, distributed or otherwise provided outside of the Subscriber Sites, nor may it be redistributed in any form to any person or entity (including, but not limited to, any other GDS, airline, consumer or travel agency); provided that Amadeus agrees that Amadeus Data may be used in Subscriber’s email communications to its Internet Users, such as, for example, confirmation emails and weekly deals emails to Internet Users.

6. INTELLECTUAL PROPERTY

6.1 Subscriber hereby acknowledges that the Amadeus System and the Software are Amadeus’ proprietary information whether or not any portion thereof is or may be validly copyrighted or patented.

6.2 Any and all intellectual and other proprietary rights to the Amadeus System and the Software, Equipment, documentation and know-how related thereto constitutes Amadeus’ or its licensors intellectual property.

6.3 Amadeus will retain ownership of all Amadeus Software, including any new versions, enhancements or modifications as may be developed by Amadeus and made available to Subscriber. In the event Amadeus performs any additional services under Section 3.3.2, ownership of any intellectual property created pursuant to such SOW shall be as set forth in the SOW.

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6.4 Subscriber shall take the same security measures to protect the Software that Subscriber uses to protect its own confidential and proprietary information, but in no event less than the use of reasonable efforts to protect the Software from unauthorized disclosure or use.

6.5 The parties undertake, at their own costs, to perform all further acts and things and execute and deliver all further documents, reasonably requested by the other party, to vest in the requesting party the full benefit of the right, title and interest expressed as being owned by the requesting party in any intellectual property pursuant to this Section 6 (including any position on ownership agreed between the parties pursuant to Section 6.3 above in relations to any intellectual property created pursuant to any additional services) or Section 11 below.

7. CHARGES and PAYMENT

7.1 Charges

The Charges are defined in Attachment A to this Agreement.

7.2 Late Payment

If any undisputed sum payable under the Agreement is not paid by the due date. Amadeus shall be entitled to charge Subscriber interest on such sum, at the rate of 2 percentage points above the three month Euribor rate effective on that value date. Such interest shall be charged on any unpaid amounts from and including the first value date until the date of payment of the amount due.

8. TAXES

8.1 Except as otherwise set forth in this Clause, each party is responsible for and must pay any taxes for which that party is assessed in relation to the fulfilment of this Agreement.

8.2 Charges are exclusive of VAT which shall be chargeable to Subscriber at the then current rate if Amadeus is subject to VAT for the supply of goods or services to Subscriber. If VAT is chargeable to Subscriber, Subscriber shall pay such VAT together with the respective Charges for the Services that have given rise to the obligation to pay VAT.

8.3 The parties agree to use reasonable endeavours to do everything required by the relevant VAT legislation to enable or assist the other party to claim or verify any input tax credit, set off, rebate or refund in respect of any VAT paid or payable in connection with Services under this Agreement.

8.4 Should Subscriber be required under any applicable Law to withhold or deduct any portion of the payments due to Amadeus, then the sum payable to Amadeus will be increased by the amount necessary to yield to Amadeus an amount equal to the sum it would have received had no withholdings or deductions been made.

9. WARRANTIES & INDEMNITIES

9.1 Warranties

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Amadeus makes no warranties under this agreement including, without limitation, any warranty or representation with respect to any Software or any other product or service provided under or in connection with this Agreement, any express or implied warranty of merchantability or fitness for a particular purpose, accuracy and completeness of the data derived from the system, non-infringement, or any implied warranties arising out of course of performance, course of dealing or usage of trade, or that Amadeus will make the data of any particular provider available to Subscriber on the Amadeus System.

9.2 Indemnities

9.2.1 General

(a) Each party shall indemnify and defend the other party and its Affiliates and its and their officers, directors, employees, agents, representatives, successors and assignees against any and all liabilities, damages, awards, losses, costs and expenses, including court costs and reasonable attorneys’ fees (“Losses”) arising out of any claim, demand, suit or cause of action brought by a third party (“Third Party Claim”) relating to or arising from any breach by the indemnifying party of its confidentiality obligations under Article 11 (including Losses arising from any unauthorized disclosure of Confidential Information by the indemnifying party).

(b) Amadeus shall indemnify and defend Subscriber and its Affiliates and its and their officers, directors, employees, agents representatives, successor and assignees against any and all Losses arising out of any Third Party Claim that any use by Subscriber in accordance with this Agreement of the Software, the Amadeus System or any other materials supplied by Amadeus pursuant to this Agreement infringes any intellectual property rights of such Third Party.

(c) Subscriber shall indemnify and defend Amadeus and its Affiliates and its and their officers, directors, employees, agents, representative, successor and assignees against any and all Losses arising out of any Third Party Claim that any use by Subscriber other than in accordance with this Agreement infringers any intellectual property rights of such Third Party.

9.2.2 Exclusions

The Indemnitor shall have no liability under the indemnity granted above to the extent that any Third Party Claim arises as a result of:

(a) modifications made by the Indemnitee or its sub-contractors;

(b) the Indemnitee’s combination of the Indemnitor’s work product, software or materials with items not provided for under this Agreement;

(c) a breach of this Agreement by the Indemnitee; or

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(d) failure of the Indemnitee immediately to use corrections or Modifications provided by the Indemnitor offering equivalent features and functionality (except where the correction or Modification provided by the Indemnitor does not relate to such failure).

9.2.3 Consequences of IPR Infringement

Amadeus may, in its sole discretion, perform one or more of the following to minimize or eliminate the disturbance to Subscriber’s business activities, if it becomes aware of any Claim for IPR infringement under this Agreement:

(a) obtain for Subscriber the right to continue using any infringing materials, equipment or software; or

(b) modify the item(s) in question so that it is no longer infringing, and the relevant Indemnitee shall implement any such Modifications immediately; or

(c) replace such item(s) with a non-infringing replacement item without loss of functionality, and the Subscriber shall implement any such replacements immediately

9.2.4 If any party entitled to indemnification under this section (an “Indemnified Party”) makes an indemnification request to the other, the Indemnified Party shall permit the other party (the “Indemnifying Party”) to control the defense, disposition or settlement of the matter at its own expense; provided that the Indemnifying Party shall not, without the consent of the Indemnified Party, enter into any settlement or agree to any disposition that imposes any conditions or obligations on the Indemnified Party (other than the payment of monies that are immediately paid by the Indemnifying Party pursuant to the reimbursement obligations of the Indemnifying Party) or affect the rights of the Indemnified Party. Counsel selected by the Indemnifying Party shall be reasonably acceptable to the Indemnified Party. The Indemnified Party shall notify the Indemnifying Party promptly within 10 business days after receipt of any claim or as soon thereafter as reasonably practicable, for which the Indemnifying Party is responsible and shall reasonably cooperate with the Indemnifying Party to facilitate the defense of any such claim. An Indemnified Party shall at all times have the option to participate in any Claim through counsel of its own selection and at its own expense.

10. LIMITATION OF LIABILITY

IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR FOR ANY DAMAGES RESULTING FROM LOSS OF USE, DATA, OPPORTUNITY OR PROFITS, WHETHER IN CONTRACT, TORT, STRICT LIABILITY OR OTHERWISE (AND WHETHER SUFFERED BY THE PARTY, ITS AFFILIATES OR CUSTOMERS), EVEN IF SUCH PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. IN NO EVENT SHALL EITHER PARTY’S LIABILITY TO THE OTHER PARTY FOR DAMAGES IN CONNECTION WITH THIS AGREEMENT IN THE AGGREGATE EXCEED THE AMOUNT OF FEES PAID BY KAYAK TOAMADEUS DURING THE 12 MONTHS PRECEDING THE FIRST CLAIM PURSUANT TO THIS AGREEMENT, WHETHER IN CONTRACT, TORT, STRICT LIABILITY OR OTHERWISE. THE LIMITATIONS CONTAINED IN THIS SECTION

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SHALL NOT APPLY TO THE PARTIES’ INDEMNIFICATION OBLIGATIONS SET FORTH IN SECTION 9, A BREACH BY EITHER PARTY OF SECTION 11 (CONFIDENTIALITY), A BREACH BY KAYAK OF SECTION 7 (CHARGES) OR LIABILITIES FOR WILFUL MISCONDUCT, FRAUD OR DEATH OR PERSONAL INJURY.

11. CONFIDENTIALITY

The Parties will not disclose any of the terms and conditions of this Agreement, including but not limited to pricing or Incentive terms, to any third party without other Party’s written consent. Further, both Parties agree not to disclose the other Party’s Confidential Information without written consent except as otherwise required by law (including or in connection with a public offering of shares of stock). “Confidential Information” includes the terms and conditions of this Agreement and otherwise means information, not generally known in the relevant trade or industry, which was received by a Party (the “Receiving Party”) from the other Party (the “Disclosing Party”), and which is information relating to: (1) trade secrets of the Disclosing Party (including, without limitation, the source code and object code of the Software); (2) existing or contemplated products, services, technology, designs, processes, formulae, computer systems, algorithms, research or developments of the Disclosing Party; or (3) business plans, sales or marketing methods, methods of doing business, customer lists or requirements, and supplier information of the Disclosing Party. “Confidential Information” does not include information (1) already known to the Receiving Party at the time of disclosure (unless under a pre-existing obligation of confidence); (2) that becomes publicly available (other than due to a breach by the Receiving Party); (3) is rightfully received by the Receiving Party from a third party without an obligation of confidentiality; (4) is independently developed by the Receiving Party without reference to the Disclosing Party’s Confidential Information, or (5) relates to data generated through the System which is disclosed by Amadeus to or as required by third parties in the normal and customary course of Amadeus’ business. Amadeus understands and acknowledges that Kayak, in the course of its business may (i) manage, modify, maintain and update pre-existing data and information about Internet Users for use with the Amadeus System and/or Software, and (ii) generate, manage, modify, maintain and update such additional data and information (such pre-existing data and information and such additional data and information are referred to collectively as “Kayak Data”; provided that schedule, fare and availability data used by the Amadeus System and/or Software, the MetaPricer Queries submitted to the Amadeus System, and the responses thereto shall not constitute Kayak Data). Kayak shall retain all right, title and interest in and to all Kayak Data. In no event shall Amadeus be permitted access to any Kayak Data containing personally identifiable information regarding Internet Users. Notwithstanding anything to the contrary herein, all such Kayak Data consisting of, without limitation, transactional or financial information, Internet User names and addresses, passwords, registration information, and cookie information, shall be subject to Kayak’s privacy policy as set forth on the Subscriber Sites, and Kayak shall not provide any such data to Amadeus.

12. TERMINATION/EFFECT OF TERMINATION

12.1 Termination

In addition to any other termination rights expressly provided for in this Agreement, this Agreement may be terminated by either Party (i) for a material breach of any term of the Agreement by the other Party, in the event that the other Party fails to cure such breach

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within thirty (30) days after receipt of notice; or (ii) upon notice if the other Party breaches Section 11 above and fails to cure all consequences arising from such breach within five (5) days notice of the breach; or (iii) as otherwise expressly provided in this Agreement; or (iv) the Service Levels to be included as Attachment C are not agreed and initialled by the Parties within forty-five (45) days of the Signature Date of the Agreement; or (iv) if the other party becomes insolvent, makes an assignment for the benefit of creditors, suffers the appointment of a receiver, a trustee, a creditors committee, or a petition in bankruptcy or seeks reorganization, or readjustment of its debts or its dissolution or liquidation or for any other relief under any bankruptcy or insolvency law, or has entered against it a judgement or decree for its dissolution which remains undismissed or undischarged or unbonded for a period of thirty (30) days, or if the other Party shall take any step leading to the cessation as a going concern, or ceases operations for reasons other than a strike, or (v) a Force Majeure event, or (vi) as may be provided by applicable regulatory law.

Notwithstanding the foregoing, if the parties jointly develop a solution to replace MetaPricer, the parties anticipate amending or replacing this Agreement.

12.2 Effect of Termination.

In the event of termination of this Agreement, the Parties will promptly return all Confidential Information to the Disclosing Party,

13. NOTICES

NOTICES AND CONSENTS UNDER THIS AGREEMENT MUST BE IN WRITING, AND WILL BE DEEMED DELIVERED: (1) FIVE BUSINESS DAYS AFTER BEING SENT BY FIRST CLASS MAIL TO THE ADDRESS BELOW (OR IDENTIFIED ON THE FORM ATTACHED AS EXHIBIT 1); OR (2) TWO BUSINESS DAYS AFTER BEING SENT BY WAY OF A NATIONALLY RECOGNIZED OVERNIGHT DELIVERY SERVICE TO THE ADDRESS BELOW (OR IDENTIFIED ON THE FORM ATTACHED AS EXHIBIT 1); OR (3) IMMEDIATELY UPON HAND DELIVERY OR EMAILING, IN EACH CASE TO THE PERSON IDENTIFIED BELOW.

To: Amadeus   Same address as above.   Attn: Director, Leisure and Online Travel   For any claims hereunder, a copy to General Counsel. To: Kayak   Same address as above.   Attn: Chief Commercial Officer   For any claims hereunder, a copy to General Counsel.

Either Party may give written notice to the other Party of such other address(es) to which notices shall be sent, and thereafter notices shall be sent to such new or additional addresses.

14. ARBITRATION

14.1 Any question concerning the existence, validity, or termination of this Agreement, and any other dispute arising out of or relating to this Agreement, that cannot be resolved by agreement between the Parties shall be finally settled by arbitration according to the ICC Rules and the following:

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14.2 The number of arbitrators shall be three. Each Party shall nominate one arbitrator for confirmation by the ICC. If a Party fails to nominate an arbitrator within the time period specified by the ICC Rules, the ICC Court of Arbitration shall appoint an arbitrator for that Party. The arbitrators nominated by (or on behalf of) the Parties shall, within twenty one (21) days after their confirmation by the ICC Court of Arbitration, agree on a third arbitrator who shall act as the chairman.

14.3 The language of the arbitration shall be English.

14.4 The decision of the arbitrators shall be final, conclusive and binding on the Parties. Any award rendered by the arbitrators may be enforced by any court or authority of competent jurisdiction.

14.5 The place of the arbitration shall be London, England.

14.6 Any monetary award shall be denominated in USD.

14.7 The arbitrators shall be bound to follow the terms and conditions of this Agreement including, but not limited to, all limitations of liability provided herein.

15. GENERAL PROVISIONS

15.1 Assignment. Subscriber may not assign this Agreement or any right or obligation under this Agreement without Amadeus’ consent. If Amadeus permits an assignment, the assignee will be deemed to have assumed and be bound by all of Subscriber obligations under this Agreement. Amadeus may assign this Agreement to (i) a company within the Amadeus Group, and (ii) to any entity that acquires substantially all of Amadeus’ assets.

15.2 Force Majeure. Neither Party shall be responsible for, nor be deemed to be in default under this Agreement on account of, any failure to perform or delay in performance hereunder caused directly or indirectly by any fact beyond such Party’s reasonable control including, but not limited to, acts of God, war, terrorism, criminal acts of third parties, embargo, strikes or, work stoppage riots, civil unrest, fires or acts of government (“Force Majeure”). The Party claiming that Force Majeure has occurred shall without unnecessary delay notify the other Party in writing of the cause and effect of the Force Majeure. The Parties shall use their best efforts to avoid, overcome and offset the effects of any cause or potential cause of an event of Force Majeure. The Party claiming Force Majeure shall notify the other Party immediately of the cessation of the Force Majeure. Upon cessation of the cause of the Force Majeure, this Agreement shall again become fully operative up to the original term of the agreement. In the event any Force Majeure continues beyond 60 days, either Party shall have the right to terminate this Agreement without any pecuniary liability.

15.3 Governing Law. This Agreement is governed by and construed in accordance with the laws of England.

15.4 Public Communications. All public communications that mention both Parties shall be mutually agreed upon. The Parties will work together to draft a joint press release to be issued following the execution of the Definitive Agreement.

15.5 Waiver. No waiver of any provision or of any breach of this Agreement shall constitute a waiver of any other provision or of any subsequent breach.

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15.6 Independence. In no event shall either Party act as an agent of the other. The Parties are entirely independent from the other and this Agreement in no manner creates a partnership, joint venture or similar relationship.

15.7 Entire Agreement / Modification. This Agreement constitutes the entire agreement between the Parties with respect to this subject matter and supersedes and cancels all prior agreements or understandings, oral or written, including that certain Term Sheet entered into between the parties effective 3 November 2006, as amended. This Agreement may not be modified or amended except in writing, signed by authorized representatives of each Party.

15.8 Third Party Beneficiary. This Agreement is for the benefit of the Parties only. It does not confer any rights or benefits on any other party including any Franchisee.

15.9 Severability. If any provision of this Agreement shall be invalid, illegal, or unenforceable in any respect, it shall be ineffective only to the extent of such invalidity, illegality or unenforceability and shall not in any way affect or impair the validity, legality and enforceability of the balance of such provision or any other provision of this Agreement. The Parties shall endeavour in good faith negotiations to replace the invalid, illegal or unenforceable provision(s) or such portion thereof with such valid, legal and enforceable provision(s) the economic effect or which is as close as possible to that of the invalid, illegal or unenforceable provision(s).

15.10 Captions. The captions appearing in this Agreement have been inserted as a matter of convenience and in no way define, limit or enlarge the scope of any provision of this Agreement.

15.11 Counterparts. This Agreement may be executed in one or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

15.12 Quarterly Status Meeting. Each party shall designate representatives to attend a quarterly status meeting to review performance and discuss on-going collaboration.

IN WITNESS THEREOF, the Parties hereto have executed this Agreement as of the day and year first below written.

Amadeus IT Group, S.A.		KAYAK Software Corporation
Name:	Stephane Durand	Name:	Keith Melnick
Title: Date:	Director, Leisure & Online 3 April 2012	Title: Date:	Chief Commercial Officer 3 April 2012
/s/ Stephane Durand		/s/ Keith Melnick
Signature		Signature

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Attachment A – Charges

1. MetaPricer

1.1 MetaPricer Fees

(a) Kayak will pay a MetaPricer Query fee based on the number of MetaPricer Queries as set out below (the “MetaPricer Query Charge”).

(b) Up to a monthly average of [            ]* Split Queries per MetaPricer Query can be sent to Amadeus, such monthly average to be measured on a rolling quarterly basis; provided that this provision does not apply to [            ]*.

(c) Kayak will pay the MetaPricer Query Charge for [            ]*.

(d) For all non-North America Domestic Queries and Split Queries, Kayak will pay a premium of [            ]* over the MetaPricer Query Charge as set forth below.

1.1.1 Non North America Domestic Queries will be charged at the following rates until [            ]* or such earlier time as Amadeus [            ]* (“the Interim Period”):

Queries per month Non US Domestic	0 to 1,000,000	1,000,001 to 3,000,000	3,000,001 to 6,000,000	6,000,001 to 12,000,000	12,000,001 to 20,000,000	20,000,001 and above
MetaPricer Query Charge	[        ]*	[        ]*	[        ]*	[        ]*	[        ]*	[        ]*
Premium price for non-North America Domestic Queries and Split Queries (up to [        ]* split queries per MetaPricer Query)	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge

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For the avoidance of doubt, the charges above will apply according to their volume level. For example, a monthly volume of [          ]* million transactions will generate [            ]* million transactions in the first column prices, and [            ]* million in the second column prices.

No volume queries from North America Domestic Queries will contribute to the table bands above.

1.1.2 North America Domestic Queries will be charged at the following rates during the Interim Period:

Per MetaPricer Query for North America Domestic Queries = [            ]*

Per MetaPricer Query for North America Domestic Split Queries (up to [            ]* Split Queries per MetaPricer Query) = [            ]*

Up to a monthly average of [            ]* North America Domestic Split Queries per MetaPricer Query can be sent to Amadeus, such monthly average to be measured on a rolling quarterly basis. The total excess North America Domestic Split Queries per MetaPricer Query per month will be divided by [            ]*, and the remainder will be charged as per the applicable MetaPricer Query charge.

1.1.3 All MetaPricer Queries (both North America Domestic and Non-North America) after the Interim Period:

Queries per month	0 to 2,000,000	2,000,001 to 5,000,000	5,000,001 to 10,000,000	10,000,001 to 20,000,000	20,000,001 to 30,000,000	30,000,001 and above
MetaPricer Query Charge	[        ]*	[        ]*	[        ]*	[        ]*	[        ]*	[        ]*
Premium price for non-North America Domestic Queries and Split Queries (up to [            ]* split queries per MetaPricer Query)	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge	[        ]* over the MetaPricer Query Charge

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For the avoidance of doubt, the charges above will apply according to their volume level. For example, a monthly volume of [          ]* million transactions will generate [            ]* million transactions in the first column prices, and [            ]* million in the second column prices.

Each column above will be allotted the corresponding percentage of North America Domestic Queries and Non-North America Domestic Queries according to the ratio between them in that month. For example, where a monthly volume of [            ]* million transactions consists of [            ]* North America Domestic Queries and [            ]* Non-North America Domestic Queries,
[            ]* of the first column volume will be assigned to North American Domestic Queries and [            ]* will be assigned to Non-North American Domestic Queries.

1.2 Minimum Fees

Kayak will guarantee minimum fees as set forth below:

	2012		2013		2014		2015
Minimum fees per year		[        ]* million		[        ]* million		[        ]* million		[        ]* million

1.3 Excess Query Fee

Up to a monthly average of [            ]* Split Queries per MetaPricer Query can be sent to Amadeus, such monthly average to be measured on a rolling quarterly basis. The total excess Split Queries per MetaPricer Query per month will be divided by [            ]*, and the remainder will be charged as per the applicable MetaPricer Query charge.

2. [            ]*

[            ]* will be charged as follows:

[            ]* price:

[            ]* Split Queries per month = [            ]*

[            ]* Split Queries per month = [            ]*

The monthly fee related to the first two months of live production usage will be waived. In the event Kayak needs more than [          ]* MetaPricer Queries per month, the parties will meet to discuss a new monthly fee which, once agreed, will be documented in an Amendment to this Agreement. Likewise, if Subscriber requires the use of the [            ]* solution beyond the [            ]*, the parties will meet to discuss a replacement solution.

3. Amadeus Web Services pricing

3.1 Ongoing Fees

A monthly fee of [            ]* will be charged per Application for the use of Amadeus Web Services, with transaction reporting and help desk support included. However, for any month that Kayak pays more than the monthly minimum fees as defined in Article 1.2 above, these Amadeus Web Services Ongoing fees will be waived.

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Attachment B

Amadeus Web Services Agreement

ARTICLE 1: DEFINITIONS

For the purposes of this Attachment B, the following terms are defined as follows:

“Certification Schedule” means a timeframe during which Amadeus shall attempt to certify the Client Applications submitted by the Subscriber.

“Client Application User” means any legal entity that contracts (i) with Subscriber to receive a license for the Client Application in accordance with the terms of this Agreement and (ii) with Amadeus or any of its authorized affiliates or entities to receive access to the Amadeus System when using a Client Application in accordance with the terms of the applicable Access Agreement (as defined herein).

“Client Application” means any developments using the Web Services, performed by Subscriber and certified by Amadeus under the terms of this Agreement. For the avoidance of doubt, Subscriber shall maintain sole ownership, right, title and interest in the Client Application.

“Test System” means the system used to test and validate any developments by Subscriber before these developments are certified by Amadeus.

“Web Services” means the Amadeus Web Services Program and related infrastructure, including but not limited to hardware, software and services, made available by the Amadeus Group to Subscriber for the development of Client Applications, and to Client Application Users for providing access to the Amadeus System using Client Applications.

ARTICLE 2: CERTIFICATION & TEST SYSTEM ACCESS

2.1 The Client Application developed must be certified by Amadeus in accordance with the Certification Guidelines Document provided by Amadeus.

2.2 Subscriber shall receive access to the Test System under this Agreement only for the development purposes described herein (which, subject to Amadeus’ written authorization, may include performing test searches and bookings in order to determine the functionality of the Client Application) and not for any other purposes.

2.3 Upon Amadeus’ request, Subscriber shall inform Amadeus of the progress and status of the development of the Client Application.

2.4 Subscriber may subcontract the support and performance of the Client Application development work to a third-party developer; provided that (i) Subscriber first obtains Amadeus’ prior written consent; and (ii) Subscriber uses best efforts to ensure that any such designated third party subcontractor complies with all the obligations stated herein. Notwithstanding the foregoing and despite Amadeus’ consent to Subscriber’s use of

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subcontractors, Subscriber shall at all times remain liable to Amadeus for the acts and omissions of its subcontractors.

2.5 In the event that Amadeus authorizes the subcontracting of the Client Application development work, Amadeus shall deliver the Software to that designated third party contractor subject to the terms and conditions stated herein.

2.6 The Client Application shall be developed and submitted to Amadeus for Certification as further specified in the Certification Guidelines provided by Amadeus within a maximum period of one (1) year after Amadeus delivers the Software to Subscriber.

ARTICLE 3: ACCESS TO THE WEB SERVICES BY DEVELOPER

3.1 Amadeus agrees to provide Subscriber access to the Web Services under the terms and conditions described herein only for the development purposes described in this Attachment B. In the event that the establishment of a communication link between the Test System and the equipment used for development is necessary, Subscriber shall be responsible for the ordering, maintenance, use and payment of such link and the costs arising therefrom.

3.2 Subscriber shall take all reasonable precautions necessary to prevent unauthorized access to the Test System through its connection to the Web Services.

ARTICLE 4: MAINTENANCE AND SUPPORT

4.1 Amadeus’ responsibility for maintenance of the Software shall be as follows:

4.1.1 Amadeus shall provide maintenance services for only the latest release of the Software. It is the Developer’s responsibility to ensure that it is utilizing the latest version of the Software concerning new releases or updated versions of the Software is available to Developer via the Web Services Developer website.

4.2 Amadeus shall have no responsibility to provide maintenance and support for the Client Application.

4.2.1 Developer shall be responsible to Amadeus and its contracted Client Application Users for maintaining and providing support for the Client Application it has developed as well as any Client Application developed by any of its subcontractors or third party developers.

4.2.2 Amadeus shall not be responsible for providing support to the Client Application Users for problems regarding the Client Application.

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Attachment C

Service Level Agreement

To be completed in 45 days after signature date

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EX-23.2

Exhibit 23.2

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the use in this Registration Statement on Form S-1 (No. 333-170640) of KAYAK Software Corporation of our report dated March 9, 2012 relating to the financial statements and financial statement schedule of KAYAK Software Corporation, which appears in such Registration Statement. We also consent to the reference to us under the heading “Experts” in such Registration Statement.

/s/ PricewaterhouseCoopers LLP

Stamford, CT

April 20, 2012