Southwest Airlines Co. plans to expand service from New York City and Washington this year after completing a deal to lease slots from Alaska Air Group Inc. at maxed out airports.

Southwest will be able to add six round-trip flights at New York’s LaGuardia Airport and four at Ronald Reagan Washington National Airport. The 10-year lease begins in October and has been approved by the U.S. Justice Department, Alaska said Monday.

Alaska is “monetizing” valuable assets at the two airports as it ends nonstop flights to the East Coast from Dallas Love Field this fall, Alaska Chief Executive Brad Tilden said on a call with analysts to discuss first-quarter earnings.

“Flying from Dallas to LaGuardia and Reagan National, at this point in the company’s history, was not strategic,” Tilden said.

The Seattle-based carrier plans to focus on “more strategic and profitable opportunities” on the West Coast from its two gates at Love Field near downtown Dallas, said Chief Commercial Officer Andrew Harrison.

Southwest will have details “in the coming weeks” on its expanded presence in New York and Washington, Brad Hawkins, a spokesman for the Dallas-based airline, said by email.

The lease allows Alaska to regain the slots after 2028. Airlines typically battle for takeoff and landing privileges, which are granted by the U.S. Transportation Department and become available infrequently.