SCHEDULE 13D/A 0001193125-24-175123 0001364501 XXXXXXXX LIVE 1 Common Stock, par value $0.01 per share 04/03/2025 false 0001999001 83001C108 Six Flags Entertainment Corp.

8701 Red Oak Blvd. Charlotte NC 28217

Joshua Korff, P.C. (212) 446-4800 601 Lexington Avenue New York NY 10022 0001364501 N Rehan Jaffer OO N X1 0 5000000 0 5000000 5000000 N 4.98 IN The percent of class is calculated based on 100,365,503 shares of common stock, par value $0.01 per share (the "Common Stock") of the Issuer outstanding as of February 21, 2025, as reported in the Issuer's Form 10-K filed with the Securities and Exchange Commission (the "SEC") on March 3, 2025 (the "Issuer's 10-K"). 0001364412 N H Partners Management, LLC OO N DE 0 5000000 0 5000000 5000000 N 4.98 OO The percent of class is calculated based on 100,365,503 shares of Common Stock of the Issuer outstanding as of February 21, 2025, as reported in the Issuer's 10-K. Common Stock, par value $0.01 per share Six Flags Entertainment Corp. 8701 Red Oak Blvd. Charlotte NC 28217 This Amendment No. 1 to Schedule 13D amends and supplements the statement on Schedule 13D originally filed with the SEC on July 3, 2024. Item 5(a) of the Schedule 13D is hereby amended and restated as follows: The information contained in rows 11 and 13 of the cover pages of this Schedule 13D is hereby incorporated by reference. Item 5(b) of the Schedule 13D is hereby amended and restated as follows: The information contained in rows 7-10 of the cover pages of this Schedule 13D is hereby incorporated by reference. Item 5(c) of the Schedule 13D is hereby amended and restated as follows: Within the prior sixty days, the Reporting Persons have effected trades with respect to Common Stock as set forth on Exhibit 99.2. Item 5(e) of the Schedule 13D is hereby amended and restated as follows:As of April 11, 2025, the Reporting Persons ceased to beneficially own more than five percent of the outstanding shares of Common Stock. Exhibit 99.1 Joint Filing Agreement, by and among H Partners Management, LLC, and Rehan Jaffer, dated as of July 1, 2024, incorporated by reference to the Schedule 13D. Exhibit 99.2 Trade Data Rehan Jaffer /s/ Rehan Jaffer 04/11/2025 H Partners Management, LLC /s/ Rehan Jaffer 04/11/2025