Sec Form 3 Filing - BASSOUL SELIM A @ Six Flags Entertainment Corporation/NEW - 2024-07-01

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person BASSOUL SELIM A 2. Issuer Name and Ticker or Trading Symbol Six Flags Entertainment Corporation/NEW [ FUN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Executive Chair (Last) (First) (Middle) 8701 RED OAK BLVD. 3. Date of Earliest Transaction (MM/DD/YY) 07/01/2024 (Street) CHARLOTTE, NC28217 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock, par value $0.01 per share 387,178 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

< td style="text-align: center;">X Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other BASSOUL SELIM A 8701 RED OAK BLVD. CHARLOTTE, NC28217 Executive Chair Signatures /s/ Selim A. Bassoul 07/01/2024 Signature of Reporting Person Date

Explanation of Responses:

Remarks: Pursuant to the Agreement and Plan of Merger, dated as of November 2, 2023 (the "Merger Agreement"), by and among the Issuer (f/k/a CopperSteel HoldCo, Inc.), Six Flags Entertainment Corporation ("Former Six Flags), Cedar Fair, L.P. ("Cedar Fair") and CopperSteel Merger Sub, LLC, on July 1, 2024, each unit of limited partner interest of Cedar Fair was converted into the right to receive one share of common stock of the Issuer and each share of common stock of Former Six Flags was converted into the right to receive 0.58 shares of common stock of the Issuer ("Former Six Flags Conversion Ratio"). In accordance with the terms of the Merger Agreement, all equity awards held by the Reporting Person with respect to shares of common stock of Former Six Flags were converted into, as adjusted by the Former Six Flags Conversion Ratio, shares of common stock of the Issuer.Exhibit 24 - Power of Attorney, incorporated herein by reference.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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