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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-05-23</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000100517</issuerCik>
        <issuerName>United Airlines Holdings, Inc.</issuerName>
        <issuerTradingSymbol>UAL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001357855</rptOwnerCik>
            <rptOwnerName>BREWER ROSALIND G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>P. O. BOX 66100 HDQLD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60666</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Share Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2024-05-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3459</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2025-05-23</value>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3459</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3459</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each share unit represents the economic equivalent of one share of common stock. Upon vesting, the share units are settled (i) 50% in cash based on average of the high and low sale prices of a share of the Company's common stock on the date of settlement (or the average of the high and low sale prices of the common stock on the preceding trading day if the settlement date is not a trading day) and (ii) 50% in shares of the Company's common stock, with any odd or fractional units rounded toward the share units to be settled in cash.</footnote>
        <footnote id="F2">(Continued from Footnote 1) Notwithstanding the foregoing, the Reporting Person elected to defer the Reporting Person's 2024 annual director equity award into a share account pursuant to the terms of the Company's Director Equity Incentive Plan (&quot;DEIP&quot;). Therefore, all the share units granted to the Reporting Person for the 2024 annual director equity award will be settled following the Reporting Person's separation from service in accordance with the terms of the DEIP.</footnote>
        <footnote id="F3">Additional share units accrue when and as dividends are paid on the Company's common stock. The number of share units accrued will be equal to the dollar amount of dividends that would be payable if the share units were actual shares of common stock, divided by the average of the high and low sale prices of a share of the Company's common stock on the date dividends are paid.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ James Cotton for Rosalind G. Brewer</signatureName>
        <signatureDate>2024-05-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2024-05-23
0
0000100517
United Airlines Holdings, Inc.
UAL
0001357855
BREWER ROSALIND G
P. O. BOX 66100 HDQLD
CHICAGO
IL
60666
1
0
0
0
0
Share Units
2024-05-23
4
A
0
3459
0
A
2025-05-23
Common Stock
3459
3459
D
Each share unit represents the economic equivalent of one share of common stock. Upon vesting, the share units are settled (i) 50% in cash based on average of the high and low sale prices of a share of the Company's common stock on the date of settlement (or the average of the high and low sale prices of the common stock on the preceding trading day if the settlement date is not a trading day) and (ii) 50% in shares of the Company's common stock, with any odd or fractional units rounded toward the share units to be settled in cash.
(Continued from Footnote 1) Notwithstanding the foregoing, the Reporting Person elected to defer the Reporting Person's 2024 annual director equity award into a share account pursuant to the terms of the Company's Director Equity Incentive Plan ("DEIP"). Therefore, all the share units granted to the Reporting Person for the 2024 annual director equity award will be settled following the Reporting Person's separation from service in accordance with the terms of the DEIP.
Additional share units accrue when and as dividends are paid on the Company's common stock. The number of share units accrued will be equal to the dollar amount of dividends that would be payable if the share units were actual shares of common stock, divided by the average of the high and low sale prices of a share of the Company's common stock on the date dividends are paid.
/s/ James Cotton for Rosalind G. Brewer
2024-05-28