American and Delta, the U.S.’s two biggest airlines, signed a new interline agreement last week, restoring their ability to reroute stranded passengers on each other’s planes. Delta broke off the previous deal in September 2015.
Interline agreements allow airlines to route passengers on each other’s flights on a single ticket; their most common use is within alliances, where passengers may fly on more than one airline to their final destination. The other, but less-common use of interlining, is when weather, breakdowns or other factors strand passengers away from home.
Traditionally, all the U.S. ‘legacy’ carriers shared such agreements, but did not include discounters such as Spirit and Allegiant. Delta broke its tie with American in 2015, complaining that American was rebooking far more passengers than Delta, and was losing money on the deal. At that time, it asked for a premium rate on the imbalance. The airlines aren’t saying if a premium is built into the new agreement.
