An interline agreement is a commercial contract between two or more airlines that allows them to cooperate on passenger ticketing, baggage handling, and revenue sharing across their separate networks.
How It Works#
When two airlines sign an interline agreement, they agree to accept each other's tickets. A passenger can book a single itinerary that combines flights from both carriers, even though the airlines operate independently.
Baggage handling is a core part of the deal. The first airline checks the passenger's bags all the way to the final destination, even when a second carrier operates the connecting flight. Without an interline agreement, the passenger would have to collect bags, exit security, recheck, and re-screen at every carrier change.
Revenue is split between the participating airlines using a standardized billing process managed by the International Air Transport Association (IATA). IATA acts as the clearinghouse, calculating what each airline is owed for its portion of the journey.
Example in Aviation#
A traveler books a single ticket from Nairobi to Oslo. The first leg flies on a regional African carrier to Addis Ababa. The second leg continues on a European carrier to Oslo. Both airlines have an interline agreement, so one ticket covers the whole journey and bags are checked through automatically.
If the regional carrier delays the first flight and the passenger misses the connection, the receiving airline can rebook the passenger under the same ticket. This protection only exists because the interline agreement creates a shared responsibility between the two carriers.
Why It Matters#
For passengers, interline agreements turn a fragmented global airline network into something that feels seamless. A single booking, a single checked bag process, and shared rebooking protection all come from this behind-the-scenes contract.
For pilots and aviation professionals, understanding interline agreements helps explain why airlines operate the way they do commercially. Network strategy, route planning, and hub selection are all shaped by which interline partnerships a carrier holds.
Key Takeaways#
- An interline agreement lets two airlines sell and honor each other's tickets on a single itinerary.
- Bags can be checked through to the final destination across participating carriers.
- IATA manages the revenue settlement between interline partners.
- Interline agreements provide rebooking protection when a partner flight causes a missed connection.
- Interline agreements differ from codeshare agreements, which go further by allowing one airline to sell seats under its own flight number on another carrier's aircraft.