
Passenger revenue by category
	Year Ended December 31,
(in millions)	2023		2022		2021
Ticket	$	43,596	$	35,626	$	19,339
Loyalty travel awards	3,462		2,898		1,786
Travel-related services	1,851		1,694		1,394
Total passenger revenue	$	48,909	$	40,218	$	22,519

Passenger Tickets. We defer sales of passenger tickets to be flown by us or that we sell on behalf of other airlines in our air traffic liability. Passenger revenue is recognized when we provide transportation. For tickets that we sell on behalf of other airlines, we reduce the air traffic liability when consideration is remitted to those airlines. The air traffic liability primarily includes sales of passenger tickets with scheduled departure dates in the future and travel credits, which can be applied as payment toward the cost of a ticket. We periodically evaluate the estimated air traffic liability and may record adjustments in our income statement. These adjustments relate primarily to tickets that expire unused ("ticket breakage"), refunds, exchanges, transactions with other airlines and other items for which final settlement occurs in periods subsequent to the sale of the related tickets at amounts other than the original sales price.

We recognized approximately $7.4 billion, $4.2 billion and $2.2 billion in passenger revenue during the years ended December 31, 2023, 2022 and 2021, respectively, that had been recorded in our air traffic liability balance at the beginning of those periods.

As of December 31, 2023, all of our air traffic liability was recorded as a current liability. As of December 31, 2022, our air traffic liability was $8.3 billion, of which $100 million was included in other noncurrent liabilities on our balance sheet due to ticket validity extensions related to certain tickets and travel credits as of the end of 2022.

Ticket Breakage. We estimate the value of ticket breakage and recognize revenue at the scheduled flight date. Our ticket breakage estimates are primarily based on historical experience, ticket contract terms and customers’ travel behavior.

Regional Carriers. Our regional carriers include both third-party regional carriers with which we have contract carrier agreements ("contract carriers") and Endeavor Air, Inc., our wholly owned subsidiary. Our contract carrier agreements are primarily structured as capacity purchase agreements where we purchase all or a portion of the contract carrier's capacity and are responsible for selling the seat inventory we purchase. We record revenue related to our capacity purchase agreements in passenger revenue and the related expenses in regional carrier expense. See Note 10, "Commitments and Contingencies," for additional information regarding contract carrier agreements.

Loyalty travel awards revenue is related to the redemption of mileage credits ("miles") for travel. We recognize loyalty travel awards revenue in passenger revenue as miles are redeemed and transportation is provided. See below for discussion of our loyalty program accounting policies.

Travel-related services are primarily composed of services performed in conjunction with a passenger’s flight, including baggage fees, administrative fees, and on-board sales. We recognize revenue for these services when the related transportation service is provided.

Our SkyMiles loyalty program generates customer loyalty by rewarding customers with incentives to travel on Delta. This program allows customers to earn miles by flying on Delta, Delta Connection carriers and other airlines that participate in the loyalty program. When traveling, customers earn miles primarily based on the passenger's loyalty program status, fare class and ticket price. Customers can also earn miles through participating companies. Miles are redeemable by customers in future periods for air travel on Delta and other participating airlines, access to Delta Sky Club and other program awards. To facilitate transactions with participating companies, we sell miles to non-airline businesses and other airlines.

The loyalty program includes two types of transactions that are considered revenue arrangements with multiple performance obligations (1) passenger ticket sales earning miles and (2) sale of miles to participating companies.

Passenger Ticket Sales Earning Miles. Passenger ticket sales earning miles provide customers with (1) miles earned and (2) air transportation, which are each considered performance obligations. We value each performance obligation on a standalone basis. To value the miles earned, we consider the quantitative value a passenger receives by redeeming miles for a ticket rather than paying cash, which is referred to as equivalent ticket value ("ETV"). Our estimate of ETV is adjusted for miles that are not likely to be redeemed ("mileage breakage"). We use statistical models to estimate mileage breakage based on historical redemption patterns. A change in assumptions regarding the redemption activity for miles or the estimated fair value of miles expected to be redeemed could have a material impact on our revenue in the year in which the change occurs and in future years. We recognize mileage breakage proportionally during the period in which the remaining miles are actually redeemed.

We defer revenue for the miles when earned and recognize loyalty travel awards in passenger revenue as the miles are redeemed and transportation is provided. We record the air transportation portion of the passenger ticket sales in air traffic liability and recognize passenger revenue when we provide transportation or if the ticket goes unused.

Sale of Miles to Participating Companies. Customers earn miles based on their spending with participating companies, such as credit card, retail, ridesharing, car rental and hotel companies, with which we have marketing agreements to sell miles. Our contracts to sell miles under these marketing agreements have multiple performance obligations. Payments are typically due to us monthly based on the volume of miles sold during the period, and the initial terms of our marketing contracts are from one to thirteen years. During the years ended December 31, 2023, 2022 and 2021, total cash sales from marketing agreements related to our loyalty program were $6.9 billion, $5.7 billion and $4.1 billion, respectively, which are allocated to travel and other performance obligations, as discussed below.

Our most significant contract to sell miles relates to our co-brand credit card relationship with American Express. Our agreements with American Express provide for joint marketing, grant certain benefits to Delta-American Express co-branded credit card holders ("cardholders") and American Express Membership Rewards program participants, and allow American Express to market its services or products using our customer database. Cardholders earn miles for making purchases using co-branded cards, and certain cardholders may also check their first bag for free, are granted discounted access to Delta Sky Club lounges and receive priority boarding and other benefits while traveling on Delta. Additionally, participants in the American Express Membership Rewards program may exchange their points for miles under the loyalty program. We sell miles at agreed-upon rates to American Express which are then provided to their customers under the co-brand credit card program and the Membership Rewards program.

We account for marketing agreements, including those with American Express, by allocating the consideration to the individual products and services delivered. We allocate the value based on the relative selling prices of those products and services, which generally consist of award travel, priority boarding, baggage fee waivers, lounge access and the use of our brand. We determine our best estimate of the selling prices by using a discounted cash flow analysis using multiple inputs and assumptions, including (1) the expected number of miles awarded and number of miles redeemed, (2) ETV for the award travel obligation adjusted for mileage breakage, (3) published rates on our website for baggage fees, discounted access to Delta Sky Club lounges and other benefits while traveling on Delta, (4) brand value (using estimated royalties generated from the use of our brand) and (5) volume discounts provided to certain partners.

We defer the amount allocated to award travel as part of loyalty program deferred revenue and recognize loyalty travel awards in passenger revenue as the miles are redeemed and transportation is provided. Revenue allocated to services performed in conjunction with a passenger’s flight, such as baggage fee waivers, is recognized as travel-related services in passenger revenue when the related service is performed. Revenue allocated to Delta Sky Club lounge access is recognized as miscellaneous in other revenue as access is provided. Revenue allocated to the remaining performance obligations, primarily brand value, is recorded as loyalty program in other revenue as miles are delivered.

Current Activity of the Loyalty Program. Miles are combined in one homogeneous pool and are not separately identifiable. Therefore, the revenue is comprised of miles that were part of the loyalty program deferred revenue balance at the beginning of the period as well as miles that were issued during the period.

The table below presents the activity of the current and noncurrent loyalty program deferred revenue, and includes miles earned through travel and miles sold to participating companies, which are primarily through marketing agreements.


Loyalty program activity
(in millions)	2023		2022		2021
Balance at January 1	$	7,882	$	7,559	$	7,182
Miles earned	4,173		3,419		2,238
Travel miles redeemed	(3,462)		(2,898)		(1,786)
Non-travel miles redeemed	(173)		(198)		(75)
Balance at December 31	$	8,420	$	7,882	$	7,559

The timing of mile redemptions can vary widely; however, the majority of new miles have historically been redeemed within two years of being earned. The loyalty program deferred revenue classified as a current liability represents our estimate of revenue expected to be recognized in the next twelve months based on projected redemptions, while the balance classified as a noncurrent liability represents our estimate of revenue expected to be recognized beyond twelve months.

Other Revenue


	Year Ended December 31,
(in millions)	2023		2022		2021
Refinery	$	3,379	$	4,977	$	3,229
Loyalty program	3,093		2,597		1,770
Ancillary businesses	840		846		793
Miscellaneous	1,104		894		556
Total other revenue	$	8,416	$	9,314	$	6,348

Loyalty Program. This relates to revenues from brand usage by third parties and other performance obligations embedded in miles sold, which are included within the total cash sales from marketing agreements, discussed above. This also includes the redemption of miles for non-travel awards.

Operating revenue for the airline segment is recognized in a specific geographic region based on the origin, flight path and destination of each flight segment. A significant portion of the refinery segment's revenues typically consists of fuel sales to support the airline, which is eliminated in the Consolidated Financial Statements. The remaining operating revenue for the refinery segment is included in the domestic region. Our passenger and operating revenue by geographic region are summarized in the following table:


Revenue by geographic region
	Passenger Revenue						Operating Revenue
	Year Ended December 31,						Year Ended December 31,
(in millions)	2023		2022		2021		2023		2022		2021
Domestic	$	33,968	$	30,197	$	18,468	$	40,845	$	38,478	$	24,320
Atlantic	9,057		6,093		1,777		10,458		7,429		2,537
Latin America	3,798		2,889		1,873		4,292		3,334		2,284
Pacific	2,086		1,039		401		2,453		1,341		758
Total	$	48,909	$	40,218	$	22,519	$	58,048	$	50,582	$	29,899

Accounts receivable primarily consist of amounts due from credit card companies from the sale of passenger tickets, ancillary businesses, refinery sales and other companies for the purchase of miles under the loyalty program. We provide an allowance for uncollectible accounts using an expected credit loss model which represents our estimate of expected credit losses over the lifetime of the asset.

We are required to charge certain taxes and fees on our passenger tickets, including U.S. federal transportation taxes, federal security charges, airport passenger facility charges and foreign arrival and departure taxes. These taxes and fees are assessments on the customer for which we act as a collection agent and these amounts are not included in passenger revenue. We record a liability when the amounts are collected and reduce the liability when payments are made to the applicable government agency or operating carrier (i.e., for codeshare-related fees).