<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2020-06-11</periodOfReport>

    <dateOfOriginalSubmission>2020-06-15</dateOfOriginalSubmission>

    <issuer>
        <issuerCik>0001525221</issuerCik>
        <issuerName>Bristow Group Inc.</issuerName>
        <issuerTradingSymbol>VTOL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001509651</rptOwnerCik>
            <rptOwnerName>Stepanek David F.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BRISTOW GROUP INC.</rptOwnerStreet1>
            <rptOwnerStreet2>3151 BRIARPARK DRIVE, SUITE 700</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77042</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Executive Vice President, COO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-06-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2030</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.16</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21397</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">In connection with the business combination pursuant to the Agreement and Plan of Merger, dated as of January 23, 2020 (as amended on April 22, 2020) by and among Era Group Inc. (the &quot;Company&quot;), Bristow Group Inc. (&quot;Old Bristow&quot;) and Ruby Redux Merger Sub, Inc. (&quot;Merger Sub&quot;), pursuant to which Merger Sub merged with and into Old Bristow, with Old Bristow surviving as a wholly owned subsidiary of the Company (the &quot;Merger&quot;) completed on June 11, 2020 (the &quot;Closing Date&quot;), 8,333 shares of restricted stock vested on the Closing Date and 2,030 shares, reported in column 4, were withheld to cover the associated tax liability upon the vesting of a previously granted award of restricted stock.</footnote>
        <footnote id="F2">Shares reported in column 5 give effect to the 1:3 reverse stock split completed in connection with the Merger.</footnote>
    </footnotes>

    <remarks>This Form 4 amendment is being filed to correct the original Form 4 filed on June 15, 2020. The original Form 4 contained an error in column 5 in reporting the amount of securities beneficially owned by the Reporting Person.</remarks>

    <ownerSignature>
        <signatureName>/s/ Justin D. Mogford, attorney-in-fact for David F. Stepanek</signatureName>
        <signatureDate>2021-03-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
