A JetBlue Airways plane passes behind an American Airlines jet waiting to taxi at Ronald Reagan National Airport in Washington, D.C.Andrew Harrer | Bloomberg | Getty ImagesAmerican and JetBlue will stop selling seats on each other’s flights after Thursday, two months after a federal judge ruled that the airlines’ partnership in the Northeast violated antitrust laws.The judge ordered the airlines to end their more than two-year partnership, which allowed them to share passengers and revenue, and to coordinate schedules in the northeastern U.S. The airlines argued they needed to team up to better compete with rivals Delta and United at congested airports serving New York City and Boston.The Justice Department, six states and the District of Columbia sued to block that partnership, winning its case on May 20.”We are disappointed to be ending popular benefits like codesharing and reciprocal loyalty benefits,” Dave Fintzen, vice president of the Northeast Alliance at JetBlue, said in a statement. “With the court’s recent ruling and the termination of the NEA, we have to sunset them in short order.”JetBlue last week said it wouldn’t appeal the ruling so it can focus instead on its $3.8 acquisition of Spirit Airlines, a deal which the Justice Department has also challenged, though JetBlue said it didn’t agree with the judge’s ruling on the Northeast AIlliance. American, however, said it still plans to appeal the ruling on the Northeast Alliance.Earlier this week, the carriers’ websites still showed flight options on each other’s airline through the year-end holidays but such sales will only continue through July 20.Both airlines said they would work with customers with existing bookings so their plans aren’t disrupted.”This is just the first step in the wind-down process that will take place over the coming months,” American said in a release. “We will continue to work with the JetBlue team to ensure customers who have existing codeshare bookings can travel seamlessly without disruption to their travel plans.”Thursday is also the last day that customers can use American AAdvantage frequent flyer miles to book flights on JetBlue.