Interline — Interline Agreement

Interline Agreement

Interline is the foundational commercial partnership framework in aviation. It pre-dates codeshare and enables a passenger to book a journey across multiple airlines on a single ticket — a capability that underpins global air travel connectivity.

What Interline Enables

Under an interline agreement, participating airlines: accept each other's tickets, issue through boarding passes for all segments, accept through-checked baggage to the final destination, assume re-accommodation obligations if a passenger misses a connection due to a delay on the inbound segment.

Interline vs Codeshare

Interline is broader than codeshare. In a codeshare, Airline A sells seats under its own code on Airline B's flight. In an interline, Airline A and B accept each other's tickets but each operates its own flights under its own code. A codeshare is a type of partnership that usually requires an interline agreement as its foundation.

Special Prorate Agreement (SPA)

When airlines agree on interline fares, they negotiate how the total fare is divided between carriers. A Special Prorate Agreement (SPA) defines this revenue split. Without an SPA, standard IATA proration rules apply.

IATA Interline Settlement

IATA's Billing and Settlement Plan (BSP) and Interline Revenue Management processes handle the financial settlement between interline partners. Airlines submit interline billing data to IATA, which calculates and distributes net payments.