An interline agreement is the simplest partnership in the game: two airlines agree to let passengers connect between their networks on a single itinerary. Each carrier keeps flying under its own brand and its own fares; interlining just makes the cross-carrier connection possible.
What it does#
Without an agreement, the booking engine will only build connections within one airline's network. Once an interline is active, itineraries that mix your flights with your partner's start appearing in passengers' choice sets, including two- and three-leg journeys neither of you could sell alone. There is no through-branding: the passenger sees each leg under its operator's name, and each leg sells at that operator's fare. If you want your brand on the whole journey, that's a codeshare; see Codeshares.
How the money splits#
Interline revenue is shared by distance: each leg's operator receives the share of the total itinerary fare that matches its leg's share of the total distance flown. There are no negotiated rates and no signing fees: no money changes hands to set an agreement up.
Scoped or network-wide#
Agreements don't have to cover everything. When you propose one, you can scope it:
- Via airports: connections only count if the passenger transfers at one of the named airports (your hubs, typically).
- Countries: only itineraries starting and ending in the named countries qualify.
- Leave both empty and the agreement covers both networks entirely.
Setting one up#
On the Partners → Interlining page:
- Choose a partner from the airline list (the Directory has a shortcut that pre-fills the form).
- Optionally set a via-airport or country scope.
- Send the proposal. Your partner sees an Offer received row and can accept or deny; you'll see Awaiting partner until they do.
Only one live agreement can exist per pair of airlines. Either side can terminate an active agreement at any time; connections stop being offered from the next daily booking pass. AI-controlled airlines propose and accept interlines too, depending on their business model; see AI carriers.
Things that can block a proposal#
If one of the two airlines belongs to an alliance whose charter forbids external interlining, proposals outside the alliance are rejected. Alliance membership can also create interline agreements automatically; those show up on this page tagged with the alliance that produced them, and they end if the member leaves. See Joint ventures & alliances.
Interlining is the foundation the other partnerships build on: codeshares require the interline plumbing (and will create it for you when accepted), and chartered alliances are, mechanically, a bundle of member interlines plus politics.