American Airlines Group Inc. and JetBlue Airways Corp. plan to expand domestic and short-haul international flying next year under a partnership that U.S. antitrust officials are seeking to dissolve.

The expansion to 10 new cities, if it goes through as planned, will bring the carriers’ Northeast Alliance to 500 daily departures across New York’s three major airports, and to 200 daily flights out of Boston, the airlines said in a statement December 9. Flights began in 2021 under the partnership, which was challenged by the U.S. Justice Department seven months later. A federal judge is currently considering whether it violates antitrust laws.

The expansion builds on the carriers’ stance in the federal trial that the alliance will give consumers more options for flights and boost competition, challenging arguments from federal attorneys that the alliance is a virtual merger than could cost consumers more than $700 million annually in higher fares. The Justice Department has asked U.S. District Judge Leo T. Sorokin to dissolve the partnership.

The alliance allows the carriers to share routes, bookings and passengers on flights from New York’s John F. Kennedy International and LaGuardia airports, Liberty International Airport in Newark, New Jersey, and Boston’s Logan International Airport.

The airlines said the expansion will include new flights by JetBlue with nonstop service from LaGuardia to Nassau, Bahamas, and Bermuda, pending government approval. It will also bring back flights between Newark and Montego Bay, Jamaica, and expand service between Boston and Vancouver.

Sorokin has said he plans one more hearing in the case after he has considered all the evidence and legal filings. The judge hasn’t indicated when he will issue a ruling.