An American Airlines Group Inc. alliance with JetBlue Airways Corp. has placed the majority of flights by US carriers at New York’s primary airports into the hands of two major airlines, an executive from rival carrier Spirit Airlines Inc. testified Thursday.

Spirit objected to the partnership between American and JetBlue, known as the Northeast Alliance, in January 2021, filing its concerns with the US Department of Transportation. That initial complaint helped lead to a federal antitrust lawsuit, which now seeks to undo the agreement. 

John Kirby, Spirit’s vice president of network planning, said the budget airline’s opinion of the alliance hasn’t changed. 

“JetBlue is in essence now a feeder airline for American and will do what American wants it to do,” he said in federal court in Boston. “American is giving them hundreds of millions of dollars in slots and access to the world’s largest frequent flyer program.”

Hanging over the trial is JetBlue’s planned $3.8 billion acquisition of Spirit, which must also pass antitrust muster before it’s final. Kirby wasn’t asked about Spirit’s pending purchase in his testimony. A lawyer for the Justice Department testified Tuesday that the acquisition would allow American “to co-opt two disruptive competitors for the price of one.” 

JetBlue’s all-cash bid derailed a planned merger of Spirit and Frontier Group Holdings Inc., which would have combined the nation’s two largest ultra-low-cost carriers.

JetBlue has taken over the use of some slots, or US authorizations for flights, held by American at John F. Kennedy and LaGuardia airports, using its larger planes to replace regional jets American had flying many of the routes. The combined American and JetBlue, along with Delta Air Lines Inc, control 84% of the flight slots at Kennedy based on December 2019 numbers, Kirby said. They also operate 81% of flight slots at LaGuardia Airport, according to the same data. 

Slots controlled by larger carriers have kept Spirit from securing enough space for a viable operation at Kennedy for a decade, Kirby said. Spirit has secured additional flight gates at LaGuardia.

That type of market concentration is behind claims by the US Justice Department that JetBlue and American’s alliance violates antitrust laws and gives the two airlines too much control in the US Northeast. The carriers claim the tie-up, which allows the companies to share routes, bookings, and passengers, gives them the substance to compete more effectively against Delta and United Airlines Holdings Inc.