UPDATE 2-Delta, US Airways in big NY, DC slot swap

* Delta, US Airways agree to slot swap

* Delta to double nonstop destinations from LaGuardia

* US Airways says deal will earn $75 million a year (Recasts. Adds US Airways president, background, AirTran/Continental, share prices)

By Kyle Peterson

CHICAGO, Aug 12 (Reuters) - Delta Air Lines Inc (DAL.N) and US Airways Group Inc (LCC.N) have agreed to a significant swap of takeoff and landing rights at New York LaGuardia and Washington Reagan National airports, the airlines said on Wednesday.

The unusually large deal has been in the works for some time and continues the efforts by US Airways to reorganize its route structure and potentially expand overseas.

Delta's objective is to enhance its New York operation as a destination for business travel and expand links to international flights.

"Really this is about getting the assets in the hands of airlines that can use them most efficiently," US Airways President Scott Kirby told Reuters.

U.S. antitrust and transportation regulators must sign off on the planned exchange of airport slots, which equal access for roundtrip flights.

Industry consultants knowledgeable about the deal said Justice Department officials would look closely at the plan for US Airways to boost operations at Reagan National, where it is already the dominant carrier.

The airlines would also have to convince Transportation Department regulators to end a recent ban on slot sales at LaGuardia.

The deal, the second of its kind involving big U.S. airlines two days, is structured as "two simultaneous asset sales" but no cash will be exchanged, the companies said.

Delta shares were up 3.3 percent at $7.25, while US Airways shares were up 4.5 percent at $3.04 in afternoon trade on the New York Stock Exchange.

The deal would transfer 125 pairs of slots from US Airways to Delta at LaGuardia. Those slots are currently used by US Airways Express.

US Airways has been criticized for underutilizing the space over the years by flying regional jets instead of larger planes. Delta plans to use bigger aircraft.

More efficient use of LaGuardia, notorious for congestion and delays, has long been a priority of transportation and aviation regulators.