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. 23)*

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

July 2, 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. 23 (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”), Amendment No. 15 filed on May 22, 2013 (“Amendment No. 15”), Amendment No. 16 filed on May 24, 2013 (“Amendment No. 16”), Amendment No. 17 filed on May 28, 2013 (“Amendment No. 17”), Amendment No. 18 filed on May 29, 2013 (“Amendment No. 18”), Amendment No. 19 filed on May 30, 2013 (“Amendment No. 19”), Amendment No. 20 filed on June 3, 2013 (“Amendment No. 20”), Amendment No. 21 filed on June 6, 2013 (“Amendment No. 21”) and Amendment No. 22 filed on June 11, 2013 (“Amendment No. 22”).

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

On July 3, 2013, CFL sent a letter to the stockholders of the Issuer (the “July 3 Letter to Stockholders”). In the July 3 Letter to Stockholders, CFL informed the stockholders of the Issuer of its withdrawal of its solicitation of proxies. A copy of the July 3 Letter to Stockholders is attached hereto as Exhibit 2, which is incorporated herein by reference. The description herein of the July 3 Letter to Stockholders is qualified in its entirety by reference to the July 3 Letter to Stockholders.

On July 2, 2013, CFL, DTN LNG, DTN Investments, Mr. John M. Howland, Mr. Eric E. Stoerr, the Halim Daniel Trust, Mr. Halim Daniel and Uniteg (collectively, the “Crest Stockholders”) and, for limited purposes, CIC, the Jamal and Rania Daniel Trust, Mr. Jamal Daniel, Mrs. Rania Daniel, the Daria Daniel Trust, the Thalia Daniel Trust, the Naia Daniel Trust, Mr. Michael Wheaton, solely in his capacity as trustee of the Halim Daniel Trust, and Crest Switzerland (collectively, the “13D Parties”) entered into a voting and sale agreement with Sprint Nextel Corporation (“Sprint”) and, for limited purposes, Starburst II, Inc. (“Starburst”) and the Issuer (the “Voting and Sale Agreement”). A copy of the Voting and Sale Agreement is attached hereto as Exhibit 3, which is incorporated herein by reference. The description herein of the Voting and Sale Agreement is qualified in its entirety by reference to the Voting and Sale Agreement.

Pursuant to the Voting and Sale Agreement, the Crest Stockholders have agreed, at any annual, special or other meeting of the stockholders of the Issuer called for the purpose of voting on the adoption of the Merger Agreement and Plan of Merger, dated as of December 17, 2012, and amended as of April 18, 2013, May 21, 2013 and June 20, 2013, by and among Sprint, Collie Acquisition Corp., a wholly-owned subsidiary of Sprint, and the Issuer (the “Merger Agreement”), to vote in favor of, among other things, (i) adopting the Merger Agreement; (ii) the matters to be voted upon by the Issuer’s stockholders pursuant to the Note Purchase Agreement and (iii) any proposal to adjourn or postpone the stockholders’ meeting held to adopt the Merger Agreement.

In addition, unless the effective time of the proposed merger (the “Proposed Sprint-Clearwire Merger”) of the Issuer with Sprint has previously occurred, upon the earlier of October 15, 2013 and the termination of the Merger Agreement pursuant to its terms, Sprint will promptly deliver a notice thereof to the Crest Stockholders (the “Termination Notice”). Upon the earlier of October 15, 2013 and the receipt of the Termination Notice, Sprint and the Crest Stockholders shall consummate the purchase by Sprint of all of the shares of Class A Common Stock owned by the Crest Stockholders as of July 2, 2013 and, in Sprint’s sole discretion, all or any portion of any additional shares of Class A Common Stock then beneficially owned by the Crest Stockholders, at a cash sale price per share equal to the greatest of (i) the Merger Consideration (as defined in the Voting and Sale Agreement), (ii) the highest price per share of Class A Common Stock paid or to be paid in the Proposed Sprint-Clearwire Merger (or in any similar merger, consolidation or similar transaction involving Sprint or one or more of its affiliates and the Issuer that is consummated or entered into prior to October 15, 2013 or the date of delivery of a Termination Notice) and (iii) $5.00, without interest.

The Voting and Sale Agreement will terminate upon the earliest to occur of the following: (i) the effective time of the Proposed Sprint-Clearwire Merger, (ii) the consummation of all of the sales of shares of Class A Common Stock contemplated by the Voting and Sale Agreement and (iii) the written agreement of Sprint, each of the Crest Stockholders and each of the 13D Parties. The Crest Stockholders have agreed that they will not transfer the shares of Class A Common Stock owned by them until the termination of the Voting and Sale Agreement, subject to certain exceptions. The Crest Stockholders have also agreed, within two business days, to submit requests to their brokers to withdraw any outstanding demands for appraisal under Delaware law with respect to the Proposed Sprint-Clearwire Merger and not to exercise or attempt to exercise any rights under Section 262 of the Delaware General Corporation Law.

Pursuant to the terms of the Voting and Sale Agreement, if the sale under the Voting and Sale Agreement occurs and at any time prior to the one-year anniversary of the consummation of such sale, Sprint or any of its affiliates acquires all, but not less than all, of the outstanding shares of Common Stock not held by Sprint or any of its affiliates, whether by merger, tender offer, purchase or other similar transaction at a price per share of Common Stock in excess of the price paid in the sale under the Voting and Sale Agreement, then Sprint shall pay to the Crest Stockholders, for each share of Common Stock purchased, the difference between the price per share of Common Stock paid in the sale under the Voting and Sale Agreement and the price per share of Common Stock paid in the subsequent transaction.

Pursuant to the terms of the Voting and Sale Agreement, Sprint, the Issuer and Starburst, subject to certain exceptions, agreed to forever fully, unconditionally and irrevocably release, waive and forever discharge, and not sue, the Crest Stockholders, the 13D Parties and their respective controlling persons, officers, directors, stockholders, agents, affiliates, subsidiaries, employees, attorneys, advisors, spouses, children, lineal descendants, heirs, and assigns, past, present and future (collectively, the “Crest Released Persons”) from any and all claims based on any event, fact, act, omission or failure to act by any Crest Released Person, whether known or unknown, occurring or existing prior the execution of the Voting and Sale Agreement, and arising out of or related to the Proposed Sprint-Clearwire Merger or the Merger Agreement and the Note Purchase Agreement and the transactions contemplated thereby or the matters referenced in the complaints or other pleadings filed in the Court of Chancery of the State of Delaware in the Delaware Litigation. In addition, the Crest Stockholders and the 13D Parties, subject to certain exceptions, agreed to forever fully, unconditionally and irrevocably release, waive and forever discharge, and not sue, Sprint, the Issuer, Starburst and their respective controlling persons, officers, directors, stockholders, agents, affiliates, subsidiaries, employees, attorneys, advisors and assigns, past, present and future (collectively, the “Company Released Persons”) from any and all claims based on any event, fact, act, omission or failure to act by any Company Released Person, whether known or unknown, occurring or existing prior the execution of the Voting and Sale Agreement, and arising out of or related to the Proposed Sprint-Clearwire Merger or the Merger Agreement and the Note Purchase Agreement and the transactions contemplated thereby or the matters referenced in the complaints or other pleadings filed in the Court of Chancery of the State of Delaware in the Delaware Litigation.

Pursuant to the terms of the Voting and Sale Agreement, the Crest Stockholders have agreed to deliver to Sprint or its designee all proxy cards received by the Crest Stockholders and the 13D Parties from the stockholders of the Issuer (other than the Crest Stockholders and the 13D Parties) relating to the Special Meeting, and such proxies shall be voted as indicated thereon, subject to revocation by the applicable stockholder of the Issuer.

In addition, Sprint has agreed to reimburse the Crest Stockholders for documented costs and expenses incurred in connection with Crest’s proxy solicitation up to an amount equal to $2.5 million in the aggregate.

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 July 3 Letter to Stockholders attached hereto as Exhibit 2, the Voting and Sale Agreement attached hereto as Exhibit 3, the June 11 Letter to the Board attached to Amendment No. 22 as Exhibit 2, the June 11 Press Release attached to Amendment No. 22 as Exhibit 3, the June 6 Letter to the Board attached to Amendment No. 21 as Exhibit 2, the June 6 Press Release attached to Amendment No. 21 as Exhibit 3, the May 31 Press Release attached to Amendment No. 20 as Exhibit 2, the June 3 Letter to the Board attached to Amendment No. 20 as Exhibit 3, the June 3 Board Press Release attached to Amendment No. 20 as Exhibit 4, the June 3 Letter to Sprint attached to Amendment No. 20 as Exhibit 5, the June 3 Sprint Press Release attached to Amendment No. 20 as Exhibit 6, the May 30 Letter to the Board attached to Amendment No. 19 as Exhibit 2, the May 30 Press Release attached to Amendment No. 19 as Exhibit 3, the May 28 Press Release attached to Amendment No. 18 as Exhibit 2, the May 28 FCC Letter attached to Amendment No. 18 as Exhibit 3, the May 29 Press Release attached to Amendment No. 18 as Exhibit 4, the May 28 Letter to Stockholders attached to Amendment No. 17 as Exhibit 2, the May 28 Press Release attached to Amendment No. 17 as Exhibit 3, the May 23 Press Release attached to Amendment No. 16 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: July 3, 2013

SCHEDULE A

EXECUTIVE OFFICERS AND DIRECTORS OF CERTAIN REPORTING PERSONS

The following is a list of the executive officers and directors of certain Reporting Persons, setting forth the present principal occupation or employment and the name, principal business and address of any corporation or other organization in which such employment is conducted for each such person. The current business address of each such person is JP Morgan Chase Tower, 600 Travis, Suite 6800, Houston, TX 77002. All executive officers and directors listed below are citizens of the United States of America.

Crest Financial Limited

Crest Investment Company

DTN LNG, LLC

DNT Investments, LLC

Crest Switzerland LLC

Uniteg Holding SA

EXHIBIT INDEX