American Airlines and Delta Air Lines have failed to come up with suitable terms to extent their interline agreement, meaning the courtesy will end on Sept. 15.

An interline agreement is a deal between two airlines that allows them to sell tickets on each other’s flights. It proves to be very convenient in some cases for travelers.

For example, let’s say a passenger needed to get from New York to Omaha, Nebraska, but there were no direct flights. The passenger could book a ticket on Airline A from New York to Chicago and then book a flight from Chicago to Omaha on Airline B on the same ticket.

Not anymore, at least not between American and Delta.

“We have been unable to come to terms on an agreement with Delta and, as a result, have mutually agreed to end our interline agreement effective Sept. 15,” American spokesman Casey Norton told the Dallas Morning News. “From that date, neither airline will offer interline services to each other, including the ability to rebook passengers at discounted rates on the other carrier when flight disruptions occur.”

A passenger can still book the same flights as outlined in the example above, but without the interline agreement a traveler would have to buy two separate tickets, and if he or she had checked any bags would have to claim them from the carousel, go back through security, and re-check bags for the second flight.

“While this is a change, it will not affect our commitment to re-accommodate customers during irregular operations. The new American now has the world’s largest and best network and our team is doing a great job of running a reliable airline,” Norton said. “With nine hubs and gateways and nearly 7,000 daily flights, we have more ability to re-route our customers during operational disruption than any other airline in the world.”

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