Participating Airlines
Carriers that participate in airline alliances such as Star Alliance or SkyTeam 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 carriers marketing flights 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 and is responsible for distributing the proceeds to other carriers in that itinerary, usually through an intermediary known as BSP (Billing and Settlement Plan). Taxes will also be distributed to the various government and local agencies.
Only the plating carrier is responsible for paying commission to the issuing 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 should be issued on plated on 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.
When changes need to be made to a nonrefundable interline ticket, only the plating carrier must be included in the new itinerary. Other carriers may be added or dropped as needed to build the new itinerary.
Read more about this topic: Interlining