Add seats (XML)

Seats can be bought at two moments, with the same mechanics — SeatAvailability returns priced seat offer items, and the chosen item is referenced in the committing call:

On an existing order — SeatAvailability with an OrderRequest, then OrderChange (below).
During the initial booking — SeatAvailability with an OfferRequest against the priced offer, then include the seat item in OrderCreate (further down).

The order flow continues from Make a test booking — you need a confirmed order and a valid token. Examples were captured live on v21.3; v25.4 is identical apart from the URL segment and the response <VersionNumber>.

Step 1 — SeatAvailability — get the seat map

POST /ndc/v21.3/SeatAvailability

For an existing order, SeatAvailCoreRequest takes an OrderRequest (post-booking) instead of the pre-booking OfferRequest:

IATA_SeatAvailabilityRQ
<?xml version="1.0" encoding="UTF-8"?>
<IATA_SeatAvailabilityRQ xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersMessage">
  <DistributionChain>
    <DistributionChainLink xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <Ordinal>1</Ordinal>
      <OrgRole>Seller</OrgRole>
      <ParticipatingOrg>
        <OrgID>BZ</OrgID>
      </ParticipatingOrg>
    </DistributionChainLink>
    <DistributionChainLink xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <Ordinal>2</Ordinal>
      <OrgRole>Carrier</OrgRole>
      <ParticipatingOrg>
        <OrgID>MX</OrgID>
      </ParticipatingOrg>
    </DistributionChainLink>
  </DistributionChain>
  <Request>
    <Pax xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <PaxID>ADT-1</PaxID>
      <PTC>ADT</PTC>
    </Pax>
    <SeatAvailCoreRequest xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <OrderRequest>
        <Order>
          <OrderID>MXYTG780SE6I</OrderID>
          <OwnerCode>MX</OwnerCode>
        </Order>
      </OrderRequest>
    </SeatAvailCoreRequest>
  </Request>
</IATA_SeatAvailabilityRQ>

The response has two halves:

ALaCarteOffer — one OfferItem per open seat and passenger, with an OfferItemID prefixed OFI-ST- and a UnitPrice. Capture the a-la-carte OfferID and the seat's OfferItemID for step 2.
SeatMap — the cabin per segment: CabinCompartment → SeatRow → Seat with occupation status and characteristic codes.

IATA_SeatAvailabilityRS — 200 OK (trimmed)
<?xml version="1.0" encoding="UTF-8"?>
<IATA_SeatAvailabilityRS xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersMessage">
  <Response>
    <ALaCarteOffer xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <OfferID>ALC-ST-T1J8TVhZVEc3ODBTRTZJ</OfferID>
      <OfferItem>
        <Eligibility>
          <OfferFlightAssociations>
            <PaxSegmentReferences>
              <PaxSegmentRefID>SEG-UFZVU05BfDIwMjYwOTE1fE1YMTY0NA</PaxSegmentRefID>
            </PaxSegmentReferences>
          </OfferFlightAssociations>
          <PaxRefID>ADT-1</PaxRefID>
        </Eligibility>
        <OfferItemID>OFI-ST-U3xQVlVTTkF8MjAyNjA5MTV8TVgxNjQ0fEFEVC0xfDI0RA</OfferItemID>
        <Service>
          <ServiceDefinitionRefID>SD-ST-U3xQVlVTTkF8MjAyNjA5MTV8TVgxNjQ0fDI0RA</ServiceDefinitionRefID>
          <ServiceID>SVC-ST-U3xQVlVTTkF8MjAyNjA5MTV8TVgxNjQ0fEFEVC0xfDI0RA</ServiceID>
        </Service>
        <UnitPrice>
          <TotalAmount CurCode="USD">14.00</TotalAmount>
        </UnitPrice>
      </OfferItem>
      <!-- one OfferItem per remaining open seat elided -->
    </ALaCarteOffer>
    <DataLists xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <!-- ServiceDefinitionList (one entry per seat, e.g. "Seat 24D"),
           SeatProfileList (legroom tiers) elided -->
    </DataLists>
    <SeatMap xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <CabinCompartment>
        <CabinCompartmentID>Y</CabinCompartmentID>
        <DeckCode>Main</DeckCode>
        <SeatRow>
          <RowNumber>24</RowNumber>
          <Seat>
            <ColumnID>D</ColumnID>
            <OccupationStatusCode>F</OccupationStatusCode>
            <RowNumber>24</RowNumber>
            <SeatCharacteristicCode>A</SeatCharacteristicCode>
            <SeatCharacteristicCode>RS</SeatCharacteristicCode>
            <SeatProfileRefID>SP-PITCH-31</SeatProfileRefID>
          </Seat>
          <!-- remaining seats in the row elided -->
        </SeatRow>
        <!-- remaining rows elided -->
      </CabinCompartment>
    </SeatMap>
  </Response>
  <PayloadAttributes>
    <Timestamp xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">2026-08-17T15:27:31.402Z</Timestamp>
    <VersionNumber xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">21.3</VersionNumber>
  </PayloadAttributes>
</IATA_SeatAvailabilityRS>

We'll take seat 24D at $14. The OFI-ST- ID carries identity only (segment, passenger, seat) — the price is recomputed from live booking state when accepted.

Step 2 — OrderChange — accept the seat offer

POST /ndc/v21.3/OrderChange

AcceptSelectedQuotedOfferList references the a-la-carte offer and seat item, SelectedSeat names the row and column, and PaymentFunctions pays the new balance:

IATA_OrderChangeRQ
<?xml version="1.0" encoding="UTF-8"?>
<IATA_OrderChangeRQ xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersMessage">
  <DistributionChain>
    <DistributionChainLink xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <Ordinal>1</Ordinal>
      <OrgRole>Seller</OrgRole>
      <ParticipatingOrg>
        <OrgID>BZ</OrgID>
      </ParticipatingOrg>
    </DistributionChainLink>
    <DistributionChainLink xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <Ordinal>2</Ordinal>
      <OrgRole>Carrier</OrgRole>
      <ParticipatingOrg>
        <OrgID>MX</OrgID>
      </ParticipatingOrg>
    </DistributionChainLink>
  </DistributionChain>
  <Request>
    <ChangeOrderChoice xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <AcceptSelectedQuotedOfferList>
        <SelectedPricedOffer>
          <OfferRefID>ALC-ST-T1J8TVhZVEc3ODBTRTZJ</OfferRefID>
          <SelectedOfferItem>
            <OfferItemRefID>OFI-ST-U3xQVlVTTkF8MjAyNjA5MTV8TVgxNjQ0fEFEVC0xfDI0RA</OfferItemRefID>
            <PaxRefID>ADT-1</PaxRefID>
            <SelectedSeat>
              <SeatRowNumber>24</SeatRowNumber>
              <ColumnID>D</ColumnID>
            </SelectedSeat>
          </SelectedOfferItem>
        </SelectedPricedOffer>
      </AcceptSelectedQuotedOfferList>
    </ChangeOrderChoice>
    <Order xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <OrderID>MXYTG780SE6I</OrderID>
      <OwnerCode>MX</OwnerCode>
    </Order>
    <PaymentFunctions xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <PaymentProcessingDetails>
        <Amount CurCode="USD">14.00</Amount>
        <Payer>
          <PayerName>
            <IndividualName>
              <GivenName>John</GivenName>
              <Surname>Doe</Surname>
            </IndividualName>
          </PayerName>
          <PaymentAddress>
            <PostalAddress>
              <CityName>Los Angeles</CityName>
              <CountryCode>US</CountryCode>
              <CountrySubDivisionName>California</CountrySubDivisionName>
              <PostalCode>90210</PostalCode>
              <StreetText>123 Main St</StreetText>
            </PostalAddress>
          </PaymentAddress>
        </Payer>
        <PaymentMethod>
          <PaymentCard>
            <CardBrandCode>VI</CardBrandCode>
            <CardNumber>4111111111111111</CardNumber>
            <CardSecurityCode>123</CardSecurityCode>
            <ExpirationDate>1227</ExpirationDate>
          </PaymentCard>
        </PaymentMethod>
      </PaymentProcessingDetails>
    </PaymentFunctions>
  </Request>
</IATA_OrderChangeRQ>

The response is the updated IATA_OrderViewRS. The seat appears as its own OrderItem (OOI-ST- prefix) with a SeatOnLeg association, and the order total grows to $73:

IATA_OrderViewRS — 200 OK (seat order item)
      <OrderItem>
        <OrderItemID>OOI-ST-U3xQVlVTTkF8MjAyNjA5MTV8TVgxNjQ0fFBBWC1RVVJVTFRFfFNFQVR8MjRE</OrderItemID>
        <OwnerCode>MX</OwnerCode>
        <Price>
          <BaseAmount CurCode="USD">0</BaseAmount>
          <Fee>
            <Amount CurCode="USD">14</Amount>
            <DesigText>SEAT</DesigText>
          </Fee>
          <TotalAmount CurCode="USD">14</TotalAmount>
        </Price>
        <Service>
          <BookingRef>
            <BookingEntity>
              <Carrier>
                <AirlineDesigCode>MX</AirlineDesigCode>
              </Carrier>
            </BookingEntity>
            <BookingID>JE88TR</BookingID>
            <BookingRefTypeCode>6</BookingRefTypeCode>
          </BookingRef>
          <DeliveryStatusCode>CONFIRMED</DeliveryStatusCode>
          <OrderServiceAssociation>
            <SeatOnLeg>
              <Seat>
                <ColumnID>D</ColumnID>
                <RowNumber>24</RowNumber>
              </Seat>
              <SeatAssignmentAssociations>
                <PaxSegmentRef>
                  <PaxSegmentRefID>SEG-UFZVU05BfDIwMjYwOTE1fE1YMTY0NA</PaxSegmentRefID>
                </PaxSegmentRef>
              </SeatAssignmentAssociations>
            </SeatOnLeg>
          </OrderServiceAssociation>
          <PaxRefID>ADT-1</PaxRefID>
          <ServiceID>SVC-ST-U3xQVlVTTkF8MjAyNjA5MTV8TVgxNjQ0fFBBWC1RVVJVTFRFfFNFQVR8MjRE</ServiceID>
          <StatusCode>CONFIRMED</StatusCode>
        </Service>
        <StatusCode>ACTIVE</StatusCode>
      </OrderItem>

Adding a seat during the initial booking

The same seat map exists for a priced offer, before any order — so a booking can be created with its seat in one shot.

1. Get the seat map for the priced offer (after OfferPrice, before OrderCreate). The request is the one from step 1 with OfferRequest in place of OrderRequest:

IATA_SeatAvailabilityRQ (SeatAvailCoreRequest excerpt)
    <SeatAvailCoreRequest xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <OfferRequest>
        <Offer>
          <OfferID>OF-96a92874-fcbc-43bd-8c68-b1e95e88156d</OfferID>
          <OfferItem>
            <OfferItemID>OFI-96a92874-fcbc-43bd-8c68-b1e95e88156d-0-ADT</OfferItemID>
            <PaxRefID>ADT-1</PaxRefID>
          </OfferItem>
          <OwnerCode>MX</OwnerCode>
        </Offer>
      </OfferRequest>
    </SeatAvailCoreRequest>

The response is the same ALaCarteOffer + SeatMap shape as the order-scoped call above — pick the seat and capture its OfferItemID (OFI-ST-…).

2. Include the seat item in OrderCreate. Add a second SelectedOfferItem under the same SelectedPricedOffer, and pay the combined total ($59 fare + $14 seat). No SelectedSeat element is needed — the OFI-ST- ID already encodes the seat:

IATA_OrderCreateRQ (CreateOrder excerpt)
    <CreateOrder xmlns="http://www.iata.org/IATA/2015/EASD/00/IATA_OffersAndOrdersCommonTypes">
      <AcceptSelectedQuotedOfferList>
        <SelectedPricedOffer>
          <OfferRefID>OF-96a92874-fcbc-43bd-8c68-b1e95e88156d</OfferRefID>
          <OwnerCode>MX</OwnerCode>
          <SelectedOfferItem>
            <OfferItemRefID>OFI-96a92874-fcbc-43bd-8c68-b1e95e88156d-0-ADT</OfferItemRefID>
            <PaxRefID>ADT-1</PaxRefID>
          </SelectedOfferItem>
          <SelectedOfferItem>
            <OfferItemRefID>OFI-ST-U3xQVlVTTkF8MjAyNjA5MTV8TVgxNjQ0fEFEVC0xfDI0RQ</OfferItemRefID>
            <PaxRefID>ADT-1</PaxRefID>
          </SelectedOfferItem>
        </SelectedPricedOffer>
      </AcceptSelectedQuotedOfferList>
    </CreateOrder>

A seat item takes exactly one PaxRefID, and it must match the passenger the seat was priced for — use the same PaxID values (ADT-1, ADT-2, …) from AirShopping through OrderCreate so they line up. The response is the usual IATA_OrderViewRS: the order arrives OPENED with the seat as its own OOI-ST- order item, everything CONFIRMED from the start.

Notes

Moving to a different seat is the same call with the new seat's offerItemId. The swap is atomic. If allowed by rules, a portion of the previous seat fee may be credited toward the new seat.
Only BOO-generated OFI-ST-* IDs are accepted; raw seat unit keys or client-built IDs are rejected with ERR-1004.
Changes that create a positive balance require payment. A held (unpaid) order can accept updates which increases the balance due.
If the seat was reserved by a different session between the seat map call and its selection, the change is rejected. Retrieve the seat map for current availability and try again.

Full schema reference: SeatAvailability and OrderChange.

Step 1 — SeatAvailability — get the seat map​

Step 2 — OrderChange — accept the seat offer​

Adding a seat during the initial booking​

Notes​

Step 1 — SeatAvailability — get the seat map

Step 2 — OrderChange — accept the seat offer

Adding a seat during the initial booking

Notes