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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-03-29</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001270821</rptOwnerCik>
            <rptOwnerName>ISAACSON WALTER</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"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2024-03-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>841.04</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>841.04</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18025.87</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The share units convert to shares of common stock on a 1-for-1 basis.</footnote>
        <footnote id="F2">Represents 2024 quarterly retainer fees that the Reporting Person elected to defer into a share account pursuant to the terms of the Company's 2006 Director Equity Incentive Plan (&quot;DEIP&quot;).</footnote>
        <footnote id="F3">The share units will be settled in common stock following the Reporting Person's separation from service in accordance with the terms of the DEIP.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ James Cotton for Walter Isaacson</signatureName>
        <signatureDate>2024-03-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0508
4
2024-03-29
0
0000100517
United Airlines Holdings, Inc.
UAL
0001270821
ISAACSON WALTER
P. O. BOX 66100 HDQLD
CHICAGO
IL
60666
1
0
0
0
0
Share Units
2024-03-29
4
A
0
841.04
0
A
Common Stock
841.04
18025.87
D
The share units convert to shares of common stock on a 1-for-1 basis.
Represents 2024 quarterly retainer fees that the Reporting Person elected to defer into a share account pursuant to the terms of the Company's 2006 Director Equity Incentive Plan ("DEIP").
The share units will be settled in common stock following the Reporting Person's separation from service in accordance with the terms of the DEIP.
/s/ James Cotton for Walter Isaacson
2024-03-29