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. 16)*

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 23, 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. 16 (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”), Amendment No. 12 filed on May 13, 2013 (“Amendment No. 12”), Amendment No. 13 filed on May 17, 2013 (“Amendment No. 13”), Amendment No. 14 filed on May 20, 2013 (“Amendment No. 14”) and Amendment No. 15 filed on May 22, 2013 (“Amendment No. 15”).

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

On May 23, 2013, CFL and CIC (collectively, the “Participants”) filed with the Securities and Exchange Commission (the “SEC”) a supplement to its definitive proxy statement relating to the Participants’ intention to solicit proxies from the stockholders of the Issuer in connection with a special meeting of such stockholders to be held to vote upon the proposed transaction between the Issuer and Sprint-Nextel Corporation. On May 23, 2013, CFL issued a press release (the “May 23 Press Release”) relating to the filing of the supplement to its definitive proxy statement, a copy of which is attached hereto as Exhibit 2 and is incorporated herein by reference. The description herein of the May 23 Press Release is qualified in its entirety by reference to the May 23 Press Release. The supplement was mailed to the stockholders of the Issuer on or around May 24, 2013.

Item 4 of the Schedule 13D is hereby amended and supplemented by replacing the nineteenth paragraph thereof (counting the above paragraph) with the following paragraph:

The supplement to the proxy statement was mailed to the stockholders of the Issuer on or around May 24, 2013. SECURITYHOLDERS OF CLEARWIRE ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT AND THE SUPPLEMENT, 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, the supplement 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 and the supplement are also available at no charge on the website of the Participants’ proxy solicitor at http://www.dfking.com/clwr.

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 23 Press Release attached hereto as Exhibit 2, the May 21 Letter to Stockholders attached to Amendment No. 15 as Exhibit 2, the May 21 Letter to the Board attached to Amendment No. 15 as Exhibit 3, the May 21 Press Release attached to Amendment No. 15 as Exhibit 4, the May 20 Letter to Stockholders attached to Amendment No. 14 as Exhibit 2, the May 20 Letter to the Board attached to Amendment No. 14 as Exhibit 3; the May 20 Press Release attached to Amendment No. 14 as Exhibit 4, the May 17 Letter to Stockholders attached to Amendment No. 13 as Exhibit 2, the May 17 Press Release attached to Amendment No. 13 as Exhibit 3, the May 16 Letter to Stockholders attached to Amendment No. 13 as Exhibit 4, the May 16 Press Release attached to Amendment No. 13 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 24, 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 24th day of May, 2013.

Exhibit 2

FOR IMMEDIATE RELEASE:

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

Crest Supplements its Proxy Statement Opposing Revised Terms for Sprint-Clearwire Merger

HOUSTON, May 23, 2013 – Crest Financial Limited, the largest independent minority shareholder of Clearwire Corporation (NASDAQ: CLWR) with approximately 8.25% of the Class A common stock of Clearwire, today filed a supplement to its definitive proxy statement with the Securities and Exchange Commission. Crest continues to urge Clearwire stockholders to reject the proposed merger with Sprint Nextel Corporation.

Crest reiterated that it opposes the Sprint-Clearwire merger because it believes that Clearwire would be better off if it remained a stand-alone company. Sprint’s new offer of $3.40 in cash per share still significantly undervalues Clearwire – based on several measures – and was devised by Sprint in a way that unfairly disadvantages minority stockholders, Crest said. The proxy supplement also notes that Crest has been joined in its opposition to the merger by a group of other large minority Clearwire stockholders led by Mount Kellett Capital Management LP who hold approximately 18.2% of the Class A common stock of Clearwire.

Crest emphasized another reason stockholders should oppose the merger: Delaware law states that a Clearwire stockholder who votes FOR the Sprint-Clearwire merger cannot elect to exercise its appraisal rights. According to David K. Schumacher, Crest’s General Counsel: “Any vote in favor of the merger agreement would limit your range of options to recover the fair value of your shares if Sprint succeeds in its unfair bid for Clearwire. Crest has already taken all necessary steps to perfect its appraisal rights under Delaware law. This means that Crest can ask the Delaware Court of Chancery to determine the fair value of its Clearwire common stock if the Sprint-Clearwire merger is consummated and certain other conditions are satisfied. But appraisal rights are by definition individual rights. You must perfect your own appraisal rights if you are to carry on the fight for fair value in an appraisal proceeding.”

Crest has filed a lawsuit in Delaware against Sprint, Clearwire and the directors of Clearwire because Crest believes that the defendants breached their fiduciary duties by scheming to extract value from Clearwire at the expense of the minority stockholders. In addition, Crest has petitioned the Federal Communications Commission in Washington, D.C., to stop the proposed Softbank-Sprint and Sprint-Clearwire transactions because they would treat minority stockholders of Clearwire unfairly and the transactions would not be in the public’s best interest.

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 against the merger, please call D.F. King & Co. at (800) 949-2583. The full proxy statement and supplement 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 supplement to its definitive proxy statement with the U.S. Securities and Exchange Commission (“SEC”). The supplement to will be mailed to the stockholders of Clearwire on or around May 24, 2013. SECURITYHOLDERS OF CLEARWIRE ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT AND THE SUPPLEMENT, 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, the supplement 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 and the supplement are 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.

SOURCE: Crest Financial Limited