SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

[Rule 13d-101]

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(a)

AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2(a)

(Amendment No. 13)*

Clearwire Corporation

(Name of Issuer)

Class A Common Stock

(Title of Class of Securities)

18538Q105

(CUSIP Number)

David K. Schumacher

General Counsel

Crest Financial Limited

JP Morgan Chase Tower

600 Travis, Suite 6800

Houston, TX 77002

Tel: (713) 222 6900

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

Copies to:

Stephen M. Gill

Kai Haakon E. Liekefett

Vinson & Elkins LLP

First City Tower

1001 Fannin Street, Suite 2500

Houston, TX 77002

Tel: (713) 758 2222

May 16, 2013

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ¨

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (the “Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(Continued on following pages)

This Amendment No. 13 (this “Amendment”) amends and supplements the Statement on Schedule 13D (the “Schedule 13D”) of Crest Financial Limited (“CFL”), Crest Investment Company (“CIC”), the Jamal and Rania Daniel Revocable Trust (the “Jamal and Rania Daniel Trust”), Mr. Jamal Daniel, Mrs. Rania Daniel, DTN LNG, LLC (“DTN LNG”), DTN Investments, LLC (“DTN Investments”), the Daria Daniel 2003 Trust (the “Daria Daniel Trust”), the Thalia Daniel 2003 Trust (the “Thalia Daniel Trust”), the Naia Daniel 2003 Trust (the “Naia Daniel Trust”), Mr. John M. Howland, Mr. Eric E. Stoerr, the Halim Daniel 2012 Trust (the “Halim Daniel Trust”), Mr. Michael Wheaton, solely in his capacity as trustee of the Halim Daniel Trust, Mr. Halim Daniel, Uniteg Holding SA (“Uniteg”) and Crest Switzerland, LLC (“Crest Switzerland” and, together with CFL, CIC, the Jamal and Rania Daniel Trust, Mr. Jamal Daniel, Mrs. Daniel, DTN LNG, DTN Investments, the Daria Daniel Trust, the Thalia Daniel Trust, the Naia Daniel Trust, Mr. Howland, Mr. Stoerr, the Halim Daniel Trust, Mr. Wheaton, solely in his capacity as trustee of the Halim Daniel Trust, Mr. Halim Daniel, Uniteg and Crest Switzerland, the “Reporting Persons”) that was filed in respect of Clearwire Corporation (the “Issuer”) on June 1, 2012 and amended by Amendment No. 1 filed on November 7, 2012 (“Amendment No. 1”), Amendment No. 2 filed on December 18, 2012 (“Amendment No. 2”), Amendment No. 3 filed on March 13, 2013 (“Amendment No. 3”), Amendment No. 4 filed on March 20, 2013 (“Amendment No. 4”), Amendment No. 5 filed on April 4, 2013 (“Amendment No. 5”), Amendment No. 6 filed on April 9, 2013 (“Amendment No. 6”), Amendment No. 7 filed on April 11, 2013 (“Amendment No. 7”), Amendment No. 8 filed on April 23, 2013 (“Amendment No. 8”), Amendment No. 9 (“Amendment No. 9”) filed on April 25, 2013, Amendment No. 10 filed on May 7, 2013 (“Amendment No. 10”), Amendment No. 11 filed on May 9, 2013 (“Amendment No. 11”) and Amendment No. 12 filed on May 13, 2013 (“Amendment No. 12”).

Item 4 of the Schedule 13D is hereby amended and supplemented by adding the following paragraphs after the first paragraph thereof:

On May 17, 2013, CFL made available a letter to stockholders of the Issuer (the “May 17 Letter to Stockholders”) and issued a press release relating thereto (the “May 17 Press Release”). In the May 17 Letter to Stockholders, CFL explained several ways it believes that the Issuer could improve its financial position if the stockholders of the Issuer reject the proposed merger with Sprint Nextel Corporation (the “Proposed Sprint-Clearwire Merger”). A copy of the May 17 Letter to Stockholders is attached hereto as Exhibit 2 and a copy of the May 17 Press Release is attached hereto as Exhibit 3, each of which are incorporated herein by reference. The descriptions herein of the May 17 Letter to Stockholders and the May 17 Press Release are qualified in their entirety by reference to the May 17 Letter to Stockholders and the May 17 Press Release.

On May 16, 2013, CFL made available a letter to stockholders of the Issuer (the “May 16 Letter to Stockholders”) and issued a press release relating thereto (the “May 16 Press Release”). In the May 16 Letter to Stockholders, CFL detailed why it is asking stockholders of the Issuer to reject the Proposed Sprint-Clearwire Merger. A copy of the May 16 Letter to Stockholders is attached hereto as Exhibit 4 and a copy of the May 16 Press Release is attached hereto as Exhibit 5, each of which are incorporated herein by reference. The descriptions herein of the May 16 Letter to Stockholders and the May 16 Press Release are qualified in their entirety by reference to the May 16 Letter to Stockholders and the May 16 Press Release.

Item 6 of the Schedule 13D is hereby amended and restated in its entirety as follows:

        Other than Asset Purchase Agreement as described in Item 3 hereof (which has been fully performed by the parties thereto in 2004), the Joint Filing Agreement attached hereto as Exhibit 1, the May 17 Letter to Stockholders attached hereto as Exhibit 2, the May 17 Press Release attached hereto as Exhibit 3, the May 16 Letter to Stockholders attached hereto as Exhibit 4, the May 16 Press Release attached hereto as Exhibit 5, the Press Release attached to Amendment No. 12 as Exhibit 2, the Presentation to Stockholders attached to Amendment No. 11 as Exhibit 2, the Press Release attached to Amendment No. 11 as Exhibit 3, the Press Release attached to Amendment No. 10 as Exhibit 2, the Letter to Stockholders attached to Amendment No. 10 as Exhibit 3, the Power of Attorney for the Daria Daniel Trust attached to Amendment No. 10 as Exhibit 4, the Power of Attorney for the Thalia Daniel Trust attached to Amendment No. 10 as Exhibit 5, the Power of Attorney for the Naia Daniel Trust attached to Amendment No. 10 as Exhibit 6, the Power of Attorney for John M. Howland attached to Amendment No. 10 as Exhibit 7, the Press Release attached to Amendment No. 9 as Exhibit 2, the Power of Attorney for the Jamal and Rania Daniel Trust attached to Amendment No. 9 as Exhibit 3, the Power of Attorney for Jamal Daniel attached to Amendment No. 9 as Exhibit 4, the Power of Attorney for Rania Daniel attached to Amendment No. 9 as Exhibit 5, the Power of Attorney for Eric E. Stoerr attached to Amendment No. 9 as Exhibit 6, the Power of Attorney for the Halim Daniel Trust attached to Amendment No. 9 as Exhibit 7, the Power of Attorney for Halim Daniel attached to Amendment No. 9 as Exhibit 8, the Power of Attorney for Michael Wheaton attached to Amendment No. 9 as Exhibit 9, the Power of Attorney for Uniteg attached to Amendment No. 9 as Exhibit 10, the Board Letter attached to Amendment No. 8 as Exhibit 2, the April 23 Press Release attached to Amendment No. 8 as Exhibit 3, the April 22 Press Release attached to Amendment No. 8 as Exhibit 4, the FCC Letter attached to Amendment No. 8 as Exhibit 5, the Press Release attached to Amendment No. 7 as Exhibit 2, the Press Release attached to Amendment No. 6 as Exhibit 2, the FCC Letter attached to Amendment No. 6 as Exhibit 3, the Letter to the Board attached to Amendment No. 5 as Exhibit 2, the April 3 Press Release attached to Amendment No. 5 as Exhibit 3, the Demand Letter attached to Amendment No. 4 as Exhibit 2, the March 20 Press Release attached to Amendment No. 4 as Exhibit 3, the March 12 Press Release attached to Amendment No. 3 as Exhibit 2, the FCC Letter attached to Amendment No. 3 as Exhibit 3, the Press Release attached to Amendment No. 2 as Exhibit 2, the Stockholder Letter attached to Amendment No. 1 as Exhibit 2 and the Press Release attached to Amendment No. 1 as Exhibit 3, neither the Reporting Persons nor, to the best of the Reporting Persons’ knowledge, any person named on Schedule A hereto, has any contracts, arrangements, understandings or relationships (legal or otherwise) among the persons named in Item 2 and between such persons and any person with respect to any securities of the Issuer, including but not limited to, transfer or voting of any of the securities, finder’s fees, joint ventures, loan or option arrangements, puts or calls, guarantees of profits, division of profits or loss, or the giving or withholding of proxies.

The following documents are filed as exhibits:

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: May 17, 2013

EXHIBIT INDEX

Exhibit 1

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of each of them of a statement on Schedule 13D (including amendments thereto) with respect to the Class A Common Stock of Clearwire Corporation and further agree that this Joint Filing Agreement be included as an Exhibit to such joint filings. In evidence thereof, the undersigned, being duly authorized, have executed this Joint Filing Agreement this 17^th day of May, 2013.

Exhibit 2

CREST FINANCIAL LIMITED

JPMorgan Chase Tower

600 Travis, Suite 6800

Houston, Texas 77002

May 17, 2013

Dear Fellow Clearwire Stockholders:

In our letter dated May 15, 2013, Crest Financial Limited (“Crest”) explained a number of reasons why you should vote AGAINST the proposed merger (the “Sprint-Clearwire Merger”) of Clearwire Corporation (“Clearwire” or the “Company”) with Sprint Nextel Corporation (“Sprint”). As we said in that letter and on other occasions, Sprint’s offer grossly undervalues Clearwire and its spectrum assets.

Many of you may be asking yourselves what will happen to Clearwire after you and the other Clearwire stockholders vote AGAINST the Sprint-Clearwire Merger? In our public statements and correspondence with our fellow stockholders, we have shown a number of different paths forward for Clearwire. Today, we want to focus on one in particular, which we mentioned in our May 15 letter: After we reject the Sprint-Clearwire Merger, the true bidding for Clearwire may begin, and therefore the Clearwire board of directors (the “Clearwire Board”) would be required to conduct a real and transparent process to seek direct bids for 100% of the Clearwire shares—whether those bids are from SoftBank Corp. (“SoftBank”), DISH Network (“DISH”), or another suitor. As we will explain further below, we believe that there are several scenarios that can be imagined in which direct bidding for Clearwire could occur.

In our May 15 letter, we discussed the bidding war underway between SoftBank and DISH for control of Clearwire’s valuable wireless spectrum. As we noted, SoftBank and DISH have not been bashful about their desire for Clearwire. SoftBank’s CEO Masayoshi Son has publicly proclaimed that, “in the Sprint-SoftBank transaction, Clearwire’s spectrum is the key.” At the same time, DISH Chairman Charlie Ergen has been equally transparent in his quest for Clearwire. Like SoftBank’s chief executive, Mr. Ergen “see[s] huge value in Sprint-Clearwire.” In fact, DISH initially bid directly for Clearwire. As Mr. Ergen recently explained, DISH “would have liked to acquire Clearwire in its entirety, obviously, but unbeknownst to [DISH], they’d sold control to Sprint,” and he also said that the reason DISH made its offer to acquire Sprint was because DISH concluded that, after dealing with the Clearwire Board, “there’s really no way to acquire [Clearwire] without acquiring Sprint” and it accordingly shifted its interest to Sprint.

As we further explained, this bidding war is not taking place through direct bids for Clearwire, which would benefit all of Clearwire’s stockholders. Instead, it is currently taking place through competing offers for Sprint. However, we envision scenarios where this quickly changes and Clearwire becomes the direct target of the suitors looking to acquire control of Clearwire’s valuable spectrum. After we the stockholders have rejected Sprint’s unfair offer, the Clearwire Board will be free to terminate the Sprint-Clearwire merger agreement, consider direct bids from DISH, SoftBank, or others for 100% of Clearwire, and recommend in favor of such a direct bid. At that time, the merger agreement itself will no longer constrain the Clearwire Board’s consideration of such alternatives. And Sprint will not have the ability under any other agreement, including the Equityholders’ Agreement, to prevent the Clearwire Board from considering and recommending

such alternatives. Such alternatives promise to turn what has been an unfair unilateral deal process with Sprint into a competitive process for Clearwire. For that to happen, however, we the stockholders need to reject the Sprint merger. And the Clearwire Board needs to rebuff subsequent incremental bids by Sprint, which will only be obstacles to thwart alternative offers. We believe that competitive process to be the only way through which we Clearwire stockholders would realize its true value.

The scenarios we envision arise from a simple question—that is, what will DISH or SoftBank do if it is not the winning bidder for Sprint?

Scenario #1—Sprint Board Rejects DISH Offer/Accepts SoftBank Offer: If the Sprint board of directors rejects DISH’s recent offer and continues forward with SoftBank, how would DISH respond? It is public knowledge that DISH now has significant capital available to pursue alternatives for spectrum. We believe that it is not beyond reason, particularly given DISH’s prior actions, that DISH could use this capital to make another, perhaps firmer, direct bid for 100% of Clearwire.

Scenario #2—Sprint Board Rejects SoftBank Offer/Accepts DISH Offer: If the Sprint board of directors decides that DISH’s recent offer is superior to the SoftBank offer and elects to terminate Sprint’s merger agreement with SoftBank, what does SoftBank do? It is not farfetched to imagine a scenario where SoftBank, instead of increasing its offer for Sprint, takes the termination fee that Sprint would be required to pay and submits a direct bid for 100% of Clearwire.

How this could play out is anybody’s guess, but one thing is for sure: it will not play out before the contest for Sprint is settled. Before then, we the Clearwire shareholders need to hold firm and reject Sprint’s attempt to lockdown Clearwire for cheap. Surely there are countless other scenarios regarding Sprint’s fate or an acquisition of Clearwire that could present themselves and that would benefit Clearwire’s minority shareholders. However, what we do know is this: Unless we all vote AGAINST the Sprint-Clearwire Merger, we Clearwire stockholders will not have the opportunity to see whether DISH, SoftBank, or another suitor, would make an offer for Clearwire that ultimately could benefit all Clearwire stockholders.

If any of these scenarios were to play out, the Clearwire Board would be under heightened scrutiny to obtain an offer that is in the best interests of all Clearwire shareholders, not just Sprint. As we all know, the Clearwire Board owes fiduciary duties to all of the Clearwire stockholders, not just Sprint, and those fiduciary duties are heightened in situations where the Company is for sale. We believe that, if Clearwire stockholders do reject the Sprint-Clearwire Merger, the spotlight on the Clearwire Board and its activities will be even brighter

As we have explained in other public disclosures, we believe that the value of Clearwire’s spectrum increases every day with the advent and development of the TDD-LTE technology that can utilize the same spectrum that Clearwire holds. We believe this is one reason why both SoftBank and DISH desperately want to control Clearwire’s spectrum. We therefore believe that, if the scenarios we suggest become real, the Company could receive bids that reflect the true value of the Company, which, in our view, far exceeds the $2.97 per share that Sprint has offered. Moreover, if the Company were to attract bids in excess of the price Sprint has offered, the Clearwire Board would be duty bound to pursue the offer and ultimately recommend that the Clearwire stockholders accept the offer. Indeed, if the Clearwire Board believes that Sprint’s

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$2.97 per share offer is a fair price, we believe that it must conclude that any price higher than that is even better for Clearwire’s stockholders.

We also believe that the Clearwire Board would have to make this recommendation to support a higher price for Clearwire shares even if Sprint is the majority stockholder and even if Sprint has indicated that it is not an interested seller. Sprint’s controlling position in Clearwire does not relieve the Clearwire Board of its fiduciary duty to seek the best price it can get for Clearwire in a sale, including if that means looking beyond Sprint as the only possible suitor for Clearwire.

Some may argue that our possible scenarios will not play out for one simple fact: Sprint will not sell its shares in Clearwire. Indeed, we understand that Sprint cannot be forced to sell its stake in Clearwire. However, we can envision a scenario where Sprint could be a seller. This could occur if bids for Clearwire were high enough to convince the Sprint board of directors that, in exercising their fiduciary duties, a sale of Sprint’s Clearwire stock is in the best interests of Sprint and its stockholders. We could envision a scenario in which such a decision was a rational outcome. If this circumstance were to present itself to the Sprint board of directors, it could determine that Sprint could carry on its current business without controlling Clearwire. Such a determination could be based on the following: Sprint would have already received a significant influx of cash (over $3 billion) from SoftBank. In addition, Sprint would receive a significant amount of additional cash through the sale of its Clearwire shares, which would provide Sprint with an opportunity to reduce its debt and gain additional liquidity. And, finally, Sprint would still have access to Clearwire’s spectrum through its existing 4G MVNO Agreement with Clearwire.

On the other hand, if Sprint were to prevent a sale of the Company, we ask you: What does that say about Sprint’s assertions regarding the value of Clearwire? Sprint believes that its $2.97 per share price is fair to Clearwire’s minority stockholders. If the Clearwire Board were to conduct the sales process we describe here and obtain a better offer than the Sprint offer, how could Sprint say with a straight face that such an offer is not better for Clearwire’s minority stockholders? We would say: It can’t. If Sprint were to reject another offer for Clearwire it would do so only if it were certain of one thing—that the Clearwire spectrum is much more valuable than its $2.97 per share price reflects.

Therefore, we believe that your vote AGAINST the Sprint-Clearwire Merger will allow the Clearwire Board to have another opportunity to unleash the value of Clearwire through a sales process that seeks direct bidders—that is, bidders other than its controlling stockholder Sprint—to make an offer for 100% of the Company.

*        *        *

We also want to bring to your attention two other issues for you to consider:

First, as we have stated in other public disclosures, Crest and other Clearwire stockholders have filed suit in the Delaware Court of Chancery alleging breaches of fiduciary duty by Sprint and the Clearwire Board and challenging the fairness of the Sprint-Clearwire Merger. Among the issues raised in those law suits is whether the Voting and Support Agreement should be struck down or enjoined. Recall that this is an agreement pursuant to which Intel Capital Corporation (and related entities), Comcast Wireless Investment, LLC, and BHN Spectrum Investments, LLC, who are Clearwire shareholders and, more importantly for this issue, are parties to the governing Equityholders’ Agreement, agreed to vote for the Sprint-Clearwire Merger.

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Crest continues to weight its options on how it would proceed from a litigation standpoint if the Sprint-Clearwire Merger were approved. As we have noted in the past, the presiding judge in the pending litigation has said that “I think there are colorable claims here.” We also believe that this judge recognized that there are circumstances in which a transaction can be rescinded. If we do pursue our claims that the terms of the Sprint-Clearwire Merger, including this Voting and Support Agreement, were coercive and unfair to the minority stockholders, we will not hesitate to take the judge at his word and argue that the Sprint-Clearwire Merger should be rescinded based on the coercive Voting and Support Agreement and other merger terms to which the Clearwire Board inexcusably agreed.

Second, as we also have noted in some of our other public disclosures, even if the Clearwire stockholders approve the Sprint-Clearwire Merger, other important conditions must be satisfied before the Sprint-Clearwire Merger can be consummated. Approval by the Federal Communications Commission (the “FCC”) of Sprint’s and its acquirer’s taking control of Clearwire’s spectrum also must be obtained. The FCC is currently considering Sprint’s and SoftBank’s joint application to take control of Clearwire’s spectrum. However, the FCC’s approval of this application is not certain. In fact, just yesterday, DISH sent a letter to the FCC asking it either to hold this proceeding in abeyance or to initiate a further evaluation by designating the SoftBank/Sprint application for a hearing. DISH’s reason for making this request is its assertion that “DISH has reportedly been the target of possible extortionate behavior on the part of SoftBank” arising from SoftBank reportedly having threatened banks that would fund DISH’s offer for Sprint with possible exclusion from participation in the planned initial public offering of the Chinese e-commerce company Alibaba Group, in which SoftBank apparently has a 33% equity stake. These allegations are serious and may give the FCC reason to delay the approval that is needed before the Sprint-Clearwire Merger can close.

*        *        *

For all of the foregoing reasons as well as the reasons stated in Crest’s proxy materials, we urge you to vote “AGAINST” the Sprint-Clearwire Merger by signing and returning the GOLD proxy card.

Crest urges all stockholders NOT to sign or return any WHITE proxy card sent to you by the Company.

If you have already returned the WHITE proxy card, you can effectively revoke it by voting the GOLD proxy card. The GOLD proxy card will provide instructions on how to vote on-line. Only your latest-dated proxy card or vote will be counted.

If you have any questions or need assistance in voting the GOLD proxy card, please contact our proxy solicitor, D.F. King & Co., Inc. at 1-800-949-2583 (toll-free). To access Crest’s definitive proxy statement at no charge, please visit the following website: http://www.dfking.com/clwr.

Sincerely yours,

/s/ David K. Schumacher

David K. Schumacher

General Counsel

Crest Financial Limited

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About Crest Financial Limited

Crest is a limited partnership under the laws of the State of Texas. Its principal business is investing in securities.

Important Legal Information

In connection with the Sprint-Clearwire Merger, Crest and other persons (the “Participants”) have filed a definitive proxy statement with the U.S. Securities and Exchange Commission (“SEC”). The definitive proxy statement has been mailed to the stockholders of Clearwire. SECURITYHOLDERS OF CLEARWIRE ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT AND ALL OTHER PROXY MATERIALS FILED WITH THE SEC, BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING ADDITIONAL INFORMATION RELATED TO THE PARTICIPANTS, CLEARWIRE, AND THE SPRINT-CLEARWIRE MERGER. The definitive proxy statement and all other proxy materials filed with the SEC are available at no charge on the SEC’s website at http://www.sec.gov. In addition, the definitive proxy statement is also available at no charge on the website of the Participants’ proxy solicitor at http://www.dfking.com/clwr.

Forward-looking Statements

Certain statements contained herein are forward-looking statements including, but not limited to, statements that are predications of or indicate future events, trends, plans, or objectives. Undue reliance should not be placed on such statements because, by their nature, they are subject to known and unknown risks and uncertainties. Forward-looking statements are not guarantees of future activities and are subject to many risks and uncertainties. Due to such risks and uncertainties, actual events may differ materially from those reflected or contemplated in such forward-looking statements. Forward-looking statements can be identified by the use of the future tense or other forward-looking words such as “believe,” “expect,” “anticipate,” “intend,” “plan,” “should,” “may,” “will,” believes,” “continue,” “strategy,” “position,” or the negative of those terms or other variations of them or by comparable terminology.

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Exhibit 3

FOR IMMEDIATE RELEASE:

CONTACT: Jeffrey Birnbaum, (202) 661-6367, JBirnbaum@BGRPR.com

Crest Financial Offers Positive Scenarios If Stockholders Block Sprint-Clearwire Merger

Urges Clearwire Stockholders to Vote Against Sprint-Clearwire Combination

HOUSTON, May 17, 2013 — Crest Financial Limited, the largest of the independent minority stockholders of Clearwire Corporation (NASDAQ: CLWR), sent a letter to Clearwire stockholders today explaining the many ways that Clearwire could improve its financial position if they reject the proposed merger with Sprint Nextel Corporation. Specifically, the letter explains that “there are several scenarios that can be imagined in which direct bidding for Clearwire could occur.”

The letter states that there is a “bidding war underway between SoftBank and DISH for control of Clearwire’s valuable wireless spectrum.” But “this bidding war is not taking place through direct bids for Clearwire, which would benefit all of Clearwire’s stockholders. Instead, it is currently taking place through competing offers for Sprint.”

However, Crest “envision[s] scenarios where this quickly changes and Clearwire becomes the direct target of the suitors looking to acquire control of Clearwire’s valuable spectrum,” if the Clearwire stockholders reject the proposed merger with Sprint. At that time, “the Clearwire Board will be free to terminate the Sprint-Clearwire merger agreement, consider direct bids from DISH, SoftBank, or others for 100% of Clearwire, and recommend in favor of such a direct bid.”

Crest further explains: “Such alternatives promise to turn what has been an unfair unilateral deal process with Sprint into a competitive process for Clearwire. For that to happen, however, we the stockholders need to reject the Sprint merger. And the Clearwire Board needs to rebuff subsequent incremental bids by Sprint, which will only be obstacles to thwart alternative offers. We believe that competitive process to be the only way through which we Clearwire stockholders would realize its true value.”

The letter then identifies potential scenarios in which Clearwire becomes the direct target of a bidding war:

“Scenario #1—Sprint Board Rejects DISH Offer/Accepts SoftBank Offer: If the Sprint board of directors rejects DISH’s recent offer and continues forward with SoftBank, how would DISH respond? It is public knowledge that DISH now has significant capital available to pursue alternatives for spectrum. We believe that it is not

beyond reason, particularly given DISH’s prior actions, that DISH could use this capital to make another, perhaps firmer, direct bid for 100% of Clearwire.

Scenario #2—Sprint Board Rejects SoftBank Offer/Accepts DISH Offer: If the Sprint board of directors decides that DISH’s recent offer is superior to the SoftBank offer and elects to terminate Sprint’s merger agreement with SoftBank, what does SoftBank do? It is not farfetched to imagine a scenario where SoftBank, instead of increasing its offer for Sprint, takes the termination fee that Sprint would be required to pay and submits a direct bid for 100% of Clearwire.”

Crest states: “How this could play out is anybody’s guess, but one thing is for sure: it will not play out before the contest for Sprint is settled. Before then, we the Clearwire shareholders need to hold firm and reject Sprint’s attempt to lockdown Clearwire for cheap. Surely there are countless other scenarios regarding Sprint’s fate or an acquisition of Clearwire that could present themselves and that would benefit Clearwire’s minority shareholders. However, what we do know is this: Unless we all vote AGAINST the Sprint-Clearwire Merger, we Clearwire stockholders will not have the opportunity to see whether DISH, SoftBank, or another suitor, would make an offer for Clearwire that ultimately could benefit all Clearwire stockholders.”

The letter adds: “If any of these scenarios were to play out, the Clearwire Board would be under heightened scrutiny to obtain an offer that is in the best interests of all Clearwire shareholders, not just Sprint. As we all know, the Clearwire Board owes fiduciary duties to all of the Clearwire stockholders, not just Sprint, and those fiduciary duties are heightened in situations where the Company is for sale. We believe that, if Clearwire stockholders do reject the Sprint-Clearwire Merger, the spotlight on the Clearwire Board and its activities will be even brighter.”

The letter also states Crest’s belief “that the value of Clearwire’s spectrum increases every day with the advent and development of the TDD-LTE technology that can utilize the same spectrum that Clearwire holds.” For this reason, Crest believes that Clearwire “could receive bids that reflect the true value of the Company, which, in [Crest’s] view, far exceeds the $2.97 per share that Sprint has offered.” Crest also explains that, “if the Clearwire Board believes that Sprint’s $2.97 per share offer is a fair price, … it must conclude that any price higher than that is even better for Clearwire’s stockholders.” And “the Clearwire Board would have to make this recommendation to support a higher price for Clearwire shares even if Sprint is the majority stockholder and even if Sprint has indicated that it is not an interested seller.”

The letter states that Crest “understand[s] that Sprint cannot be forced to sell its stake in Clearwire” but that Crest “can envision a scenario where Sprint could be a seller.” Specifically, “[t]his could occur if bids for Clearwire were high enough to convince the Sprint board of directors that, in exercising their fiduciary duties, a sale of Sprint’s Clearwire stock is in the best interests of Sprint and its stockholders.” Specifically,

Sprint’s board of directors “could determine that Sprint could carry on its current business without controlling Clearwire” based on Sprint’s already “significant influx of cash (over $3 billion) from SoftBank,” the “significant amount of additional cash through the sale of its Clearwire shares,” and the fact that “Sprint would still have access to Clearwire’s spectrum through its existing 4G MVNO Agreement with Clearwire.” Meanwhile, “[i]f Sprint were to reject another offer for Clearwire it would do so only if it were certain of one thing—that the Clearwire spectrum is much more valuable than its $2.97 per share price reflects.”

The letter raises two other issues for the stockholders’ consideration.

First, “Crest and other Clearwire stockholders have filed suit in the Delaware Court of Chancery alleging breaches of fiduciary duty by Sprint and the Clearwire Board and challenging the fairness of the Sprint-Clearwire Merger.” The letter states that “Crest continues to weigh its options on how it would proceed from a litigation standpoint if the Sprint-Clearwire Merger were approved” and notes that “the presiding judge in the pending litigation has said that ‘I think there are colorable claims here.’”

Second, the letter explains that “even if the Clearwire stockholders approve the Sprint-Clearwire Merger, … [a]pproval by the Federal Communications Commission (the ‘FCC’) of Sprint’s and its acquirer’s taking control of Clearwire’s spectrum also must be obtained.” Though the “FCC is currently considering Sprint’s and SoftBank’s joint application to take control of Clearwire’s spectrum,” the agency’s “approval of this application is not certain.” Crest’s letter notes that, “just yesterday, DISH sent a letter to the FCC asking it either to hold this proceeding in abeyance or to initiate a further evaluation by designating the SoftBank/Sprint application for a hearing” because “DISH has reportedly been the target of possible extortionate behavior on the part of SoftBank.”

Based on all this, Crest concludes that a stockholder “vote AGAINST the Sprint-Clearwire Merger will allow the Clearwire Board to have another opportunity to unleash the value of Clearwire through a sales process that seeks direct bidders—that is, bidders other than its controlling stockholder Sprint—to make an offer for 100% of the Company.”

D.F. King & Co, Inc. has been retained by Crest to assist it in the solicitation of proxies in opposition to the merger. If stockholder have any questions or need assistance in voting the GOLD proxy card, please call D.F. King & Co. at (800) 949-2583. The full letter can be found at http://www.dfking.com/clwr or http://www.bancroftpllc.com/crest.

About Crest Financial Limited

Crest Financial Limited (“Crest”) is a limited partnership under the laws of the State of Texas. Its principal business is investing in securities.

Important Legal Information

In connection with the proposed merger of Clearwire Corporation (“Clearwire”) with Sprint Nextel Corporation (the “Proposed Sprint Merger”), Crest and other persons (the “Participants”) have filed a definitive proxy statement with the U.S. Securities and Exchange Commission (“SEC”). The definitive proxy statement was mailed to the stockholders of Clearwire on or about May 6, 2013. SECURITYHOLDERS OF CLEARWIRE ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT, WHICH IS AVAILABLE NOW, AND THE PARTICIPANTS’ OTHER PROXY MATERIALS FILED WITH THE SEC WHEN THEY BECOME AVAILABLE, BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING ADDITIONAL INFORMATION RELATED TO THE PARTICIPANTS, CLEARWIRE AND THE PROPOSED SPRINT MERGER. The definitive proxy statement and all other proxy materials filed with the SEC are available at no charge on the SEC’s website at http://www.sec.gov. In addition, the definitive proxy statement is also available at no charge on the website of the Participants’ proxy solicitor at http://www.dfking.com/clwr.

Forward-looking Statements

Certain statements contained herein are forward-looking statements including, but not limited to, statements that are predications of or indicate future events, trends, plans or objectives. Undue reliance should not be placed on such statements because, by their nature, they are subject to known and unknown risks and uncertainties. Forward-looking statements are not guarantees of future activities and are subject to many risks and uncertainties. Due to such risks and uncertainties, actual events may differ materially from those reflected or contemplated in such forward-looking statements. Forward-looking statements can be identified by the use of the future tense or other forward-looking words such as “believe,” “expect,” “anticipate,” “intend,” “plan,” “should,” “may,” “will,” believes,” “continue,” “strategy,” “position” or the negative of those terms or other variations of them or by comparable terminology.

Exhibit 4

CREST FINANCIAL LIMITED

JPMorgan Chase Tower

600 Travis, Suite 6800

Houston, Texas 77002

May 15, 2013

Dear Fellow Clearwire Stockholders:

Crest Financial Limited (“Crest”), together with its affiliates and other related persons, owns approximately 8.2% of the outstanding Class A common stock of Clearwire Corporation (“Clearwire” or the “Company”) and is the largest independent, minority stockholder of Clearwire.

We have been long-time investors in Clearwire. Our investment in Clearwire dates back to June 2004 when one of our affiliates sold spectrum assets to Clearwire in exchange for shares in the Company, of which Crest received approximately 1.4 million shares. Our belief in the potential of Clearwire is demonstrated by the substantial investment we have made and maintained in the Company since that time.

Now is not the time to approve the proposed merger (the “Sprint-Clearwire Merger”) of Clearwire with Sprint Nextel Corporation (“Sprint”). As we have said repeatedly, Sprint’s offer grossly undervalues Clearwire and its spectrum assets. In addition, there is a bidding war underway between SoftBank Corp. (“SoftBank”) and DISH Network (“DISH”) for control of Clearwire’s valuable wireless spectrum. But the bidding war is not taking place through direct bids for Clearwire, which would benefit all of Clearwire’s stockholders. Instead, it is taking place through competing offers for Sprint, which will benefit only Sprint and its stockholders, because Sprint has announced that it will not approve any direct offers for Clearwire other than its own. Clearwire’s minority stockholders should not permit Sprint to divert Clearwire’s value solely to itself.

SoftBank and DISH have not been bashful about their desire for Clearwire. SoftBank’s CEO Masayoshi Son has publicly proclaimed that, “in the Sprint-SoftBank transaction, Clearwire’s spectrum is the key.” We believe SoftBank was intimately involved in Sprint’s negotiations with Clearwire for that reason. In addition, SoftBank required, as an express condition of its own proposed merger with Sprint, that Sprint purchase enough equity in Clearwire to give it control over the Clearwire Board. Sprint satisfied this condition by acquiring the Clearwire shares owned by Eagle River Investments LLC. According to Son, that is “good enough” because, even if the Sprint-Clearwire Merger fails, Sprint and its ultimate suitor could prohibit “any sales of frequency to outsiders and so on.”

But Sprint’s dominance of Clearwire is not foreordained. If you, the stockholders, reject the unfair Sprint-Clearwire Merger, and Sprint or Clearwire take any steps that harm the interests of the minority Clearwire stockholders, Crest will take the actions it believes necessary to protect its interest as one of these minority stockholders.

DISH Chairman Charlie Ergen has been equally transparent in his quest for Clearwire. Like SoftBank’s chief executive, Ergen “see[s] huge value in Sprint-Clearwire.” In fact, DISH initially bid directly for Clearwire. But that proposal was never given meaningful consideration because

Sprint expressly stated that it would not approve the deal under the Sprint-Clearwire Merger Agreement. As Ergen recently explained, DISH “would have liked to acquire Clearwire in its entirety, obviously, but unbeknownst to [DISH], they’d sold control to Sprint.” Thus, DISH concluded that “there’s really no way to acquire [Clearwire] without acquiring Sprint” and it accordingly shifted its interest to Sprint. This is a serious offer for Sprint, and through Sprint, for Clearwire. In fact, just yesterday DISH announced an approximately $2.5 billion debt offering in connection with its bid for Sprint. DISH has also confirmed that it has met with advisors to the Special Committee of the Sprint Board of Directors and responded to all questions posed by the Special Committee about the proposed takeover.

As this indirect bidding war is heating up, Clearwire’s Board of Directors has continued what we believe are its unfounded threats of insolvency and default. Clearwire has promoted the Sprint-Clearwire Transaction by suggesting that an additional $1.7 billion is needed to keep Clearwire operational and that the Sprint-Clearwire Merger is necessary to secure this additional funding. At the same time, the Company has raised the specter of missing interest payments on existing debt. But during a recent earnings call, Clearwire assured investors that “it would have enough cash to fund its operations until the first quarter of 2014,” even “if it does not raise any additional financing.” And SoftBank’s CEO Masayoshi Son has publicly stated that Sprint would prevent Clearwire from bankruptcy, even if the stockholders do not approve the Sprint-Clearwire Merger. These assurances undermine the Company’s baseless threats.

Stockholders need not accept a grossly unfair Sprint deal. The Company has alternatives to Sprint. For months, we and other stockholders have endorsed the sale of excess spectrum to enable Clearwire to improve its liquidity, pursue its build-out plans, and explore alternatives to being dominated by Sprint. DISH bid directly for Clearwire before being diverted to pursue Clearwire indirectly through its bid for Sprint. Verizon has offered to purchase spectrum leases from Clearwire. And Crest and Aurelius have offered the Company alternative financing. We believe that if the Company’s merger with Sprint is consummated, Sprint will receive all of the value that DISH, Verizon and other spectrum buyers are currently offering Clearwire and its stockholders.

We believe allowing Sprint to consummate the Sprint-Clearwire Merger will leave enormous value on the table for Clearwire stockholders—value that will assuredly be captured by Sprint and its ultimate acquirer. We believe that one way in which Sprint and its ultimate acquirer could capture this value is by using its controlling position in Clearwire to cause it to sell its excess spectrum and, instead of using these proceeds to build-out Clearwire’s network, Sprint could use these proceeds to pay down some portion of the debt that was incurred to purchase Sprint in the first place. It is no secret that both SoftBank and DISH intend to incur a significant amount of debt to purchase Sprint. Each of SoftBank and DISH also claim that it will be able to reduce this debt burden over a relatively short period of time. We believe that a sale of excess Clearwire spectrum is one way in which this de-leveraging could occur. However, we believe that Sprint and its ultimate acquirer would be able to use the excess Clearwire spectrum for this purpose ONLY IF Sprint controls 100% of Clearwire. Our view is based on the following: First, unless Sprint owns 100% of Clearwire’s stock, Clearwire could not distribute the proceeds from such a sale of spectrum to just Sprint. Second, we believe that if Sprint, through its controlling position in Clearwire, were to cause Clearwire to sell excess spectrum while litigation is pending over the conduct of Sprint, Clearwire, and the Clearwire Board, such a sale could adversely affect the position of these parties in such a proceeding if such a sale were made at the values we believe should be attributed to Clearwire’s spectrum. Thus, a successful vote “AGAINST” the

2

Sprint-Clearwire Merger would prevent Sprint from benefiting from the Clearwire spectrum assets in this way at the expense of the Clearwire stockholders.

SoftBank’s CEO Son recently said that Clearwire stockholders like Crest that have urged Clearwire to seek a better deal “can stay as shareholders for however long they want. We are happy with just 65 percent [of Clearwire stock].” For all of the reasons stated above, we do not believe this statement. We firmly believe that, if Sprint does not control 100% of Clearwire, the value that Sprint’s suitors have attached to Sprint dissipates, while, at the same time, Clearwire’s minority stockholders will still have the opportunity to realize that value for themselves.

*        *        *

In short, Clearwire is the ultimate prize in the intensifying battle for Sprint. It is time to lift the veil off of these back-to-back merger transactions so Clearwire stockholders can see them for what they are—an attempt to take value from the Clearwire stockholders without offering them fair value. We do not believe that this or any other offer from Sprint can reflect the true value of Clearwire. Only when SoftBank, DISH, or another suitor for the Clearwire spectrum makes a direct offer for the Clearwire stock or Clearwire’s assets will this true value be discovered.

As we believe, and have said in numerous public communications, all of Clearwire’s stockholders—not just its controlling stockholder, and not just Sprint’s ultimate suitor—should receive the benefit of the Company’s value. Therefore, a vote “AGAINST” the Sprint-Clearwire Merger will deny Sprint and its suitors from realizing the value of Clearwire’s spectrum at the expense of the minority stockholders unless and until a price is offered for the Clearwire shares or Clearwire’s spectrum assets that the minority stockholders believe is fair.

For all of the foregoing reasons as well as the reasons stated in Crest’s proxy materials, we urge you to vote “AGAINST” the Sprint-Clearwire Merger by signing and returning the GOLD proxy card.

Crest urges all stockholders NOT to sign or return any WHITE proxy card sent to you by the Company.

If you have already returned the WHITE proxy card, you can effectively revoke it by voting the GOLD proxy card. The GOLD proxy card will provide instructions on how to vote on-line. Only your latest-dated proxy card or vote will be counted.

If you have any questions or need assistance in voting the GOLD proxy card, please contact our proxy solicitor, D.F. King & Co., Inc. at 1-800-949-2583 (toll-free). To access Crest’s definitive proxy statement at no charge, please visit the following website: http://www.dfking.com/clwr.

Sincerely yours,

/s/ David K. Schumacher

David K. Schumacher

General Counsel

Crest Financial Limited

3

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About Crest Financial Limited

Crest is a limited partnership under the laws of the State of Texas. Its principal business is investing in securities.

Important Legal Information

In connection with the Sprint-Clearwire Merger, Crest and other persons (the “Participants”) have filed a definitive proxy statement with the U.S. Securities and Exchange Commission (“SEC”). The definitive proxy statement has been mailed to the stockholders of Clearwire. SECURITYHOLDERS OF CLEARWIRE ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT AND ALL OTHER PROXY MATERIALS FILED WITH THE SEC, BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING ADDITIONAL INFORMATION RELATED TO THE PARTICIPANTS, CLEARWIRE, AND THE SPRINT-CLEARWIRE MERGER. The definitive proxy statement and all other proxy materials filed with the SEC are available at no charge on the SEC’s website at http://www.sec.gov. In addition, the definitive proxy statement is also available at no charge on the website of the Participants’ proxy solicitor at http://www.dfking.com/clwr.

Forward-looking Statements

Certain statements contained herein are forward-looking statements including, but not limited to, statements that are predications of or indicate future events, trends, plans, or objectives. Undue reliance should not be placed on such statements because, by their nature, they are subject to known and unknown risks and uncertainties. Forward-looking statements are not guarantees of future activities and are subject to many risks and uncertainties. Due to such risks and uncertainties, actual events may differ materially from those reflected or contemplated in such forward-looking statements. Forward-looking statements can be identified by the use of the future tense or other forward-looking words such as “believe,” “expect,” “anticipate,” “intend,” “plan,” “should,” “may,” “will,” believes,” “continue,” “strategy,” “position,” or the negative of those terms or other variations of them or by comparable terminology.

4

Exhibit 5

FOR IMMEDIATE RELEASE:

CONTACT: Jeffrey Birnbaum, (202) 661-6367, JBirnbaum@BGRPR.com

Crest Financial Urges Clearwire Stockholders to Vote Against Sprint-Clearwire Merger

New Letter Highlights Scheme by Sprint to Capture Clearwire Value

HOUSTON, May 16, 2013 — Crest Financial Limited, the largest of the independent minority stockholders of Clearwire Corporation (NASDAQ: CLWR), yesterday sent a letter to Clearwire stockholders detailing why it is asking Clearwire stockholders to reject the proposed merger with Sprint Nextel Corporation.

The letter reiterates Crest’s belief that Clearwire and its trove of spectrum is “the ultimate prize in the intensifying battle for Sprint.” The Sprint effort to merge with Clearwire is really “an attempt to take value from the Clearwire stockholders without offering them fair value,” the letter states.

The letter also states:

“We believe allowing Sprint to consummate the Sprint-Clearwire Merger will leave enormous value on the table for Clearwire stockholders—value that will assuredly be captured by Sprint and its ultimate acquirer. We believe that one way in which Sprint and its ultimate acquirer could capture this value is by using its controlling position in Clearwire to cause it to sell its excess spectrum and, instead of using these proceeds to build-out Clearwire’s network, Sprint could use these proceeds to pay down some portion of the debt that was incurred to purchase Sprint in the first place. It is no secret that both SoftBank and DISH intend to incur a significant amount of debt to purchase Sprint. Each of SoftBank and DISH also claim that it will be able to reduce this debt burden over a relatively short period of time. We believe that a sale of excess Clearwire spectrum is one way in which this de-leveraging could occur. However, we believe that Sprint and its ultimate acquirer would be able to use the excess Clearwire spectrum for this purpose ONLY IF Sprint controls 100% of Clearwire. Our view is based on the following: First, unless Sprint owns 100% of Clearwire’s stock, Clearwire could not distribute the proceeds from such a sale of spectrum to just Sprint. Second, we believe that if Sprint, through its controlling position in Clearwire, were to cause Clearwire to sell excess spectrum while litigation is pending over the conduct of Sprint, Clearwire, and the Clearwire Board, such a sale could adversely affect the position of these parties in such a proceeding if such a sale were made at the values we believe should be attributed to Clearwire’s spectrum. Thus, a successful vote “AGAINST” the Sprint-

Clearwire Merger would prevent Sprint from benefiting from the Clearwire spectrum assets in this way at the expense of the Clearwire stockholders.

“SoftBank’s CEO Son recently said that Clearwire stockholders like Crest that have urged Clearwire to seek a better deal “can stay as shareholders for however long they want. We are happy with just 65 percent [of Clearwire stock].” For all of the reasons stated above, we do not believe this statement. We firmly believe that, if Sprint does not control 100% of Clearwire, the value that Sprint’s suitors have attached to Sprint dissipates, while, at the same time, Clearwire’s minority stockholders will still have the opportunity to realize that value for themselves.

“In short, Clearwire is the ultimate prize in the intensifying battle for Sprint. It is time to lift the veil off of these back-to-back merger transactions so Clearwire stockholders can see them for what they are—an attempt to take value from the Clearwire stockholders without offering them fair value. We do not believe that this or any other offer from Sprint can reflect the true value of Clearwire. Only when SoftBank, DISH, or another suitor for the Clearwire spectrum makes a direct offer for the Clearwire stock or Clearwire’s assets will this true value be discovered.”

D.F. King & Co, Inc. has been retained by Crest to assist it in the solicitation of proxies in opposition to the merger. If stockholder have any questions or need assistance in voting the GOLD proxy card, please call D.F. King & Co. at (800) 949-2583. The full letter can be found at http://www.dfking.com/clwr.

About Crest Financial Limited

Crest Financial Limited (“Crest”) is a limited partnership under the laws of the State of Texas. Its principal business is investing in securities.

Important Legal Information

In connection with the proposed merger of Clearwire Corporation (“Clearwire”) with Sprint Nextel Corporation (the “Proposed Sprint Merger”), Crest and other persons (the “Participants”) have filed a definitive proxy statement with the U.S. Securities and Exchange Commission (“SEC”). The definitive proxy statement was mailed to the stockholders of Clearwire on or about May 6, 2013. SECURITYHOLDERS OF CLEARWIRE ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT, WHICH IS AVAILABLE NOW, AND THE PARTICIPANTS’ OTHER PROXY MATERIALS FILED WITH THE SEC WHEN THEY BECOME AVAILABLE, BECAUSE THEY CONTAIN IMPORTANT INFORMATION, INCLUDING ADDITIONAL INFORMATION RELATED TO THE PARTICIPANTS, CLEARWIRE AND THE PROPOSED SPRINT MERGER. The definitive proxy statement and all other proxy materials filed with the SEC are available at no charge on the SEC’s website at http://www.sec.gov. In addition, the definitive proxy statement is also available at no charge on the website of the Participants’ proxy solicitor at http://www.dfking.com/clwr.

Forward-looking Statements

Certain statements contained herein are forward-looking statements including, but not limited to, statements that are predications of or indicate future events, trends, plans or objectives. Undue reliance should not be placed on such statements because, by their nature, they are subject to known and unknown risks and uncertainties. Forward-looking statements are not guarantees of future activities and are subject to many risks and uncertainties. Due to such risks and uncertainties, actual events may differ materially from those reflected or contemplated in such forward-looking statements. Forward-looking statements can be identified by the use of the future tense or other forward-looking words such as “believe,” “expect,” “anticipate,” “intend,” “plan,” “should,” “may,” “will,” believes,” “continue,” “strategy,” “position” or the negative of those terms or other variations of them or by comparable terminology.