Interline connectivity is the ability of different airlines to cooperate on a single passenger itinerary, issuing one ticket that covers flights operated by two or more carriers.
How It Works#
Airlines establish interline agreements with each other. These are formal contracts that allow one carrier to sell seats on another carrier's flights and issue a single itinerary covering both. The passenger checks in once and their bags transfer automatically between carriers.
When you book an interline itinerary, a single ticket record links every flight segment. Behind the scenes, the airlines exchange booking data using IATA (International Air Transport Association) messaging standards. This keeps seat reservations, baggage records, and passenger information synchronized across both carriers' systems.
Interline agreements also define how revenue splits between the airlines. Each carrier receives its agreed share of the fare, calculated using IATA proration rules. The passenger pays one price and sees none of that settlement process.
Not every airline pair has an interline agreement. If no agreement exists, the passenger must buy two separate tickets, re-check bags, and take full responsibility for making their connection.
Example in Aviation#
A traveler books a single ticket from Nairobi to a small regional airport in Canada. The first flight, operated by a large international carrier, lands in Toronto. A regional carrier then operates the final leg. Because both airlines hold an interline agreement, the travel agent issues one ticket covering both segments. The passenger checks their bags in Nairobi, and those bags transfer to the regional flight in Toronto without the passenger reclaiming them at customs.
Why It Matters#
Interline connectivity dramatically expands where airlines can send their passengers. A small regional carrier can reach global markets by partnering with a major international airline, even without flying intercontinental routes itself. This is how thin regional routes stay commercially viable.
For passengers, the practical benefit is protection. If the first flight is delayed and causes a missed connection, the issuing carrier is obligated to rebook the passenger on the next available flight at no extra cost. That protection disappears entirely with two separate tickets.
Key Takeaways#
- Interline agreements let airlines sell seats on each other's flights under one ticket.
- IATA messaging standards keep passenger and baggage data synchronized across carriers.
- Bags transfer automatically on a single interline ticket, without passenger intervention.
- One ticket means the airline is responsible for rebooking you if a connection is missed.
- Without an interline agreement, passengers must manage separate bookings independently.