Interlining is a commercial agreement between airlines that allows them to sell each other’s tickets and services to passengers on itineraries with more than one flight. This way, passengers can buy a single ticket, check in just once, have their baggage transferred to another plane, and get rebooked in case of delays or other disruptions.
Interlining can be unilateral when only one carrier within an agreement can issue tickets on a connected flight and bilateral when both airlines can issue tickets on each other’s flights.
The primary essential steps for airlines that want to participate in complex flights and cooperate with other carriers are
- enter IATA’s Multilateral Interline Traffic Agreement (MITA)
- settle and sign bilateral agreements, and
- join the IATA clearing house (ICH).
Interlining is supported by most traditional, full-service airlines, while the majority of low-cost carriers do not provide interlining flights. Members of airline alliances almost always have interlining agreements between each other.