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This article is about the airline practice. For the sewing term, see Interfacing.

Interlining (also known as "interline ticketing") is a voluntary commercial agreement between individual airlines to handle passengers traveling on itineraries that require multiple airlines.[1]


Interlining agreements differ from codesharing agreements in that codesharing agreements usually refers to numbering a flight with the airline's code (abbreviation) even though the flight is operated by another airline. However, codeshare relationships can affect whether an interline ticket (or e-ticket) can be issued. Both the codeshare marketing carrier and codeshare operating carrier must have interline agreements with all other carriers in the itinerary to allow a single ticket to be issued.

Interline agreements are directional. For example, it may be possible for American Airlines to issue the ticket on an American-United itinerary but United might not be able to be issuer on the same itinerary.

Airlines that have been established for many years are sometimes called "legacy", "network", or "full-service airlines." Previously, only large network carriers such as United Airlines and Lufthansa would have electronic ticket interline agreements but the IATA mandate to eliminate paper tickets at the end of 2007 has changed this by forcing smaller carriers to implement electronic ticketing. For example, United Airlines has an interline ticketing agreement with competitors American Airlines and British Airways. Smaller legacy carriers commonly have interline agreements with large network carriers that fly into their markets. Most newer low-cost carrier airlines that only sell directly to consumers (and not through agencies or GDS systems) do not support interlining at all. For example, United Airlines does not have an interline agreement with Southwest Airlines or Easyjet.

If no interline ticketing agreement exists (such as with Southwest and United Airlines), then two separate tickets will need to be issued and passengers will have to retrieve their bags and carry it to the connecting airline for check-in. Itineraries with interline connections such as this (whether issued on a single ticket or two tickets) are risky for travelers since the second carrier may be unaware of delays or issues with the incoming flight and it is more likely for luggage to be lost.

Most online travel agencies will only display itineraries that can be ticketed on one of their booking systems. However Orbitz will sometimes display un-ticketable interline itineraries. Examples could be found previously on routes to Mexico involving the now defunct Aero California or may be currently found on routes to Indonesia involving Lion Air. These are displayed on Orbitz as "contact airline to buy".

Participating airlines[edit]

Carriers that participate in airline alliances such as Star Alliance or Oneworld almost always have interline agreements with each other. However even direct competitors can benefit from interline agreements. When a ticket is issued for an interline itinerary, one of the airlines in that itinerary will be selected by the ticketing agent as the issuing airline, commonly referred to as the "plating carrier". The plating carrier collects the entire fare from the customer, either via own sales channels (web site or ticket office), or via travel agents. Travel agent remit collected fare and taxes to the plating carrier via ARC (Airline Reporting Corporation) in the US, or BSP (Billing and Settlement Plan) in rest of the world. The airline which actually carried the passenger (the operating airline) will send an invoice to the issuing/plating carrier, normally via IATA Clearing House, to collect its portion of fare and taxes. The operating airline is responsible for remitting passenger taxes to the various government and airports. Some taxes are sales based (US taxes), and shall be remitted by the issuing airline.

Only the issuing carrier is responsible for paying commission to the agency. The amount of commission is based on the entire air fare, although the percentage amount varies from the amount paid if only a single airline was involved.

Normal fare construction rules state that an international ticket issued should be issued by the first international carrier. There are some exceptions; for example, if the first international is a codeshare flight, the first non-codeshare would be used, or if an airline does not have an office in the country of origin.