Airline partnerships are more complex and advanced than ever before, both for better and worse. About 25 years ago the Star Alliance was formed, which was revolutionary at the time. SkyTeam and oneworld quickly joined the scene.
Continue reading: Airline Interline, Codeshare, Alliance, And Joint Venture: What Are They?
Share your questions, experiences, and thoughts below.
"For example, many years ago Delta cut its interline agreement with American. Why? At least in part it’s because Delta found that American was rebooking more passengers on Delta during irregular operations than the other way around, so the carrier no longer thought the arrangement was in its best interest."
Remember how Delta came crawling back and offering to fellate American if they would only restore that interline agreement in 2018? Karma really is a bitch.
I wish they'd all just interline. It would make life a lot easier. Think of it as customer service.
I wonder why airlines have to make codesharing so complicated (for the passenger). Just sell the damn partner flights as-is with the native flight number! The typical traveler is completely clueless, so if their flight is VS 9999, they think they're flying VS instead of DL, the operating airline.
Codeshares can wreak havoc with meal pre-orders, seat selection, upgrades, mileage earning (at least with *A, since you have no idea what the fare code will map to), etc. But often, it's your only choice if you want to book directly and avoid OTAs. So frustrating.
This was really interesting; thank you. I only started following this site recently at the recommendation of a friend. Interesting "how airlines and airplanes work" articles like this are what we keep me coming back.
There's quite some more to say about Interlining and Codesharing.
# Interlining
Interlining is the ability to sell tickets on flights from another carrier.
This can be done for pure operational reasons (e.g. DL and AA during irrops: DL can book people on AA flights, but doesn't offer this on their website).
It can also be done for commercial reasons: e.g. DL and Airlink (South Africa), for connections through JNB which can be booked on DL's website. Here, often commercial agreements are in place so the airlines together offer attractive deals.
Sometimes it is legally imposed for anti-trust reasons. Example: DE has access to LH feeder flights to FRA at attractive fares, imposed by the German government. A similar agreement exists between VS and BA at LHR.
# Code sharing
For code sharing, many more rules apply from a government point of view.
1. The carrier adding the code, must have bilateral traffic rights to the destination.
2. The carrier operating the flight, must adhere to all rules imposed by the governing agency of all carriers adding their codes.
From a passenger PoV, it is a certain safeguard for safety.
E.g.: airBaltic obtained FAA Cat 1 approval in 2023. Delta and BT only then upgraded their existing interline agreement to a codeshare agreement: https://onemileatatime.com/news/delta-airbaltic-partnership/
Other example: LH, LX, AC and ET received fines in 2024 from the FAA, as their flights crossed airspace that was prohibited by the FAA, while carried UA codeshare flight numbers.
"An interline agreement is simply a commercial agreement between airlines to handle passengers when they’re traveling on multiple airlines on the same itinerary."
Not really. An interline agreement allows a given airline to issue a ticket on another airline. As you mentioned, competitors would typically have interline agreement for disruption scenarios.
Noteworthy that the airline industry is probably the only industry having a general practice of competitors having such agreements (try asking Hertz to book you on Avis...)
Just curious, how much are airline paying for irrops on a non-partner? Full cash price? Or heavily negotiated prices?