American Airlines Group Inc. and JetBlue Airways Corp. asked a federal judge to throw out a U.S. Justice Department lawsuit challenging the airlines’ agreement to coordinate flights in the Northeast.

American and JetBlue said in a court filing Monday that their so-called Northeast Alliance has provided consumers more choices and boosted competition against Delta Air Lines Inc. and United Airlines Holdings Inc.

The alliance “has increased output in Boston and New York, including more flights to more destinations and large increases in every airline industry measure of output,” American and JetBlue said in the filing in federal court in Boston.

The airlines are fighting to save an agreement, approved by the Trump administration, in which they share revenues and coordinate flights between Boston and the New York City’s three main airports. The Justice Department, which challenged the deal in September, calls it a de-facto merger of the airlines.

The venture includes a code-sharing agreement that enables the carriers to book travelers on each other’s flights and offer reciprocal loyalty-program benefits. Passengers can use either airline’s website to buy a single itinerary that includes flights on both airlines.

In their court filing, American and JetBlue said the lawsuit is “defective” because the government hasn’t claimed the agreement has caused higher prices or a reduction in quality.

If the airlines fail to dimiss the complaint, both sides have proposed a September 2022 trial over the agreement.