Sec Form 4/A Filing - O'Donnell Shaun @ Rocket Lab USA, Inc. - 2022-09-06

FORM 4/A 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 O'Donnell Shaun 2. Issuer Name and Ticker or Trading Symbol Rocket Lab USA, Inc. [ RKLB] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP - Global Operations (Last) (First) (Middle) C/O ROCKET LAB USA, INC., 3881 MCGOWEN STREET 3. Date of Earliest Transaction (MM/DD/YY) 09/06/2022 (Street) LONG BEACH90808 4. If Amendment, Date Original Filed (MM/DD/YY) 09/08/2022 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 09/06/2022 M 724,772( 1 ) A 905,485( 3 ) 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 Restricted Stock Units ( 4 ) 09/06/2022 M 724,772 ( 4 ) ( 4 ) Common Stock 724,772 $ 0 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other O'Donnell Shaun C/O ROCKET LAB USA, INC. 3881 MCGOWEN STREET LONG BEACH90808 EVP - Global Operations Signatures /s/ Adam Spice, as Attorney-in-Factfor Shaun O'Donnell 09/09/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents 543,579 shares of common stock issued on settlement of Restricted Stock Units ("RSUs") on September 6, 2022, and 181,193 RSUs subject to service-based vesting. ( 2 )Each RSU represents a contingent right to receive one share of the issuer's common stock upon settlement. The number of shares of common stock issued on settlement on September 6, 2022 and remaining RSUs were incorrectly described in the reporting person's original Form 4. ( 3 )Includes 543,579 shares of common stock issued on settlement of RSUs on September 6, 2022; 181,193 RSUs previously reported in Table II that remain subject to service-based vesting requirements described in note 4 below; and 180,713 shares of common stock. The number of shares of common stock issued on settlement on September 6, 2022 and remaining RSUs were incorrectly described in the reporting person's original Form 4 ( 4 )The RSUs are subject to both a service-based vesting condition and liquidity-based vesting condition. The liquidity-based vesting condition was waived by the Board for these RSUs on September 6, 2022. One-sixteenth of the RSUs satisfied the service-based vesting condition at the end of each calendar quarter beginning June 30, 2019 and were settled for 543,579 shares of common stock on September 6, 2022, and the remaining RSUs will vest on the same schedule. As a result of the waiver of the liquidity-based vesting condition, the reporting person has elected to report the remaining unvested RSUs on Table I. The time-based vesting schedule for these RSUs was incorrectly described in the reporting person's original Form 4.

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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