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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-05-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001487712</issuerCik>
        <issuerName>AIR LEASE CORP</issuerName>
        <issuerTradingSymbol>AL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001752099</rptOwnerCik>
            <rptOwnerName>McCaw Susan</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AIR LEASE CORPORATION,</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, SUITE 1000N</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Air Lease Corporation - Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-05-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5565</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14900</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Restricted stock units (RSUs) granted under the Air Lease Corporation 2014 Equity Incentive Plan, in connection with the reporting person's service as a member of the Board of Directors of the Issuer. Subject to certain conditions, all of these RSUs will vest in full on May 6, 2021, the first anniversary of the grant date. Each RSU represents a contingent right to receive one share of the Issuer's Class A Common Stock on a deferred settlement date, subject to the terms of the award agreement.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Carol H. Forsyte, on behalf of Susan McCaw (Power of Attorney On File)</signatureName>
        <signatureDate>2020-05-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
