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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

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

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001709469</rptOwnerCik>
            <rptOwnerName>CORBETT ALAN</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>Senior VP, EAMEA and SAR</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-06-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>40004</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>40004</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>29.84</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2020-06-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F5"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6485</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F7"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2029-11-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6485</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6485</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>14.01</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2020-06-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F8"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20185</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F9"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2029-11-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20185</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20185</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On June 11, 2020, pursuant to the Agreement and Plan of Merger, dated as of January 23, 2020, as amended (the &quot;Merger Agreement&quot;), by and among Era Group Inc. (&quot;Era&quot;), Ruby Redux Merger Sub, Inc., a wholly owned subsidiary of Era (&quot;Merger Sub&quot;), and Bristow Group Inc. (&quot;Bristow&quot;), Merger Sub merged with and into Bristow, with Bristow continuing as the surviving corporation and a direct wholly owned subsidiary of Era (the &quot;Merger&quot;). Following the Merger, Era changed its name to Bristow Group Inc. (the &quot;Combined Company&quot;). Pursuant to the Merger Agreement, at the effective time of the Merger (the &quot;Effective Time&quot;), each holder of Bristow common stock, par value $0.0001 (&quot;Bristow Common Stock&quot;), immediately prior to the Effective Time, received, for each share of Bristow Common Stock,  0.502096 shares of Era common stock, par value $0.01 (&quot;Era Common Stock&quot;) (the &quot;Merger Consideration&quot;), and, if applicable, cash in lieu of any fractional shares. All of the issued and outstanding shares of Bristow Common Stock immediately prior to the Effective Time were cancelled.</footnote>
        <footnote id="F2">Pursuant to the Merger Agreement, each Bristow restricted stock unit (&quot;Bristow RSU&quot;) that was outstanding immediately prior to the Effective Time was, as of the Effective Time, assumed and converted into a restricted stock unit in respect of shares of Era Common Stock (&quot;Replacement RSU&quot;), in an amount based on the Merger Consideration, subject to the same terms and conditions as were applicable to the corresponding Bristow RSU immediately prior to the Effective Time.</footnote>
        <footnote id="F3">The Replacement RSUs vest in four equal annual installments beginning on November 1, 2020, subject to continuous service of the reporting person as of each such vesting date. The vested Replacement RSUs will settle on the thirtieth day following the first to occur of (i) a Change in Control (as defined in Bristow's Management Incentive Plan) and (ii) October 31, 2025.</footnote>
        <footnote id="F4">Received in exchange for 31,017 Bristow RSUs in connection with the Merger.</footnote>
        <footnote id="F5">Pursuant to the Merger Agreement, each option to purchase Bristow Common Stock that was outstanding immediately prior to the Effective Time was, as of the Effective Time, assumed and converted into an option to purchase shares of Era Common Stock (&quot;Replacement Option&quot;), subject to the same terms and conditions as were applicable to the corresponding Bristow option immediately prior to the Effective Time.</footnote>
        <footnote id="F6">The Replacement Options vest in four equal annual installments beginning on November 1, 2020, subject to continuous service of the reporting person as of each such vesting date.</footnote>
        <footnote id="F7">Received in exchange for Bristow Common Options to acquire 12,917 shares of Bristow Common Stock for $14.98 per share.</footnote>
        <footnote id="F8">Pursuant to the Merger Agreement, each option to purchase Bristow preferred stock, par value $0.0001 (&quot;Bristow Preferred Stock&quot;), that was outstanding immediately prior to the Effective Time (&quot;Bristow Preferred Option&quot;) was, immediately prior to the Effective Time, converted into a Bristow Common Option, which, as of the Effective Time, was assumed and converted into a Replacement Option, subject to the same terms and conditions as were applicable to the corresponding Bristow Preferred Option immediately prior to the Effective Time.</footnote>
        <footnote id="F9">Received in exchange for Bristow Preferred Options to acquire 7,762 shares of Bristow Preferred Stock for $36.37 per share, which were converted into Bristow Common Options immediately prior to the Effective Time.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Justin D. Mogford, Attorney-in-Fact for Alan Corbett</signatureName>
        <signatureDate>2020-06-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
