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SEC EDGAR · Insider purchase

LSTR: Lonegro Frank A reported buying shares

1 reported purchase of non-derivative securities. Code P includes open-market and private purchases; it does not establish motive.

Follow LSTR
Became public
Nov 2, 2026
Event / period date
Oct 30, 2026
Collected
Nov 8, 2026, 3:07 PM EST

Why this is connected

This filing identifies LANDSTAR SYSTEM INC as the issuer of the security. The company's SEC identifier connects it to LSTR.

Open the original source ↗Follow company activity in LSTR

Reported transactions

Lonegro Frank A (President & CEO)

5,000 shares · Common Stock

Oct 30, 2026 · $142.9238 per share

Value calculated from the reported shares and prices: $714,619.00.

Code P covers open-market and private purchases. Grants, option exercises, and tax withholding are excluded from purchase results. Read the source footnotes for ownership and pricing details.

Source evidence

Read the source excerpt or record
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-10-30</periodOfReport>

    <issuer>
        <issuerCik>0000853816</issuerCik>
        <issuerName>LANDSTAR SYSTEM INC</issuerName>
        <issuerTradingSymbol>LSTR</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001653042</rptOwnerCik>
            <rptOwnerName>Lonegro Frank A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>13410 SUTTON PARK DRIVE SOUTH</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>JACKSONVILLE</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>32224</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <officerTitle>President &amp; CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-10-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>142.9238</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>28110</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The price reported is the weighted average purchase price for the transactions reported. The prices paid ranged from $141.04 to $144.28. The reporting person will provide to the issuer, a security holder of the issuer, or the SEC staff, upon request, full information regarding the number of shares purchased at each price within the range.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Lauren W. Mapanoo, attorney-in-fact</signatureName>
        <signatureDate>2026-11-02</signatureDate>
    </ownerSignature>
</ownershipDocument>

Congressional trading in LSTR

These disclosures provide context. Their presence does not establish a link between a trader and the event.

Original documents control. Public records can be amended, and company connections may require interpretation. Nothing here is investment advice.