WASHINGTON, June 6 (Reuters) - Delta Air Lines ( DAL )

plans to announce on Thursday it will apply for a new flight

between Seattle and Washington Reagan National Airport as

airlines battle over five new daily flights.

On May 16, U.S. President Joe Biden signed legislation

creating the new flights at the busy airport in Arlington,

Virginia. The law requires the U.S. Transportation Department to

award the new flights by mid-July.

The Washington region has three major airports, but Reagan

National is the closest to the U.S. Capitol and downtown.

Because of its short runways, its main runway is the busiest in

the United States, and Reagan is the 23rd-busiest U.S. airport

by passengers.

Delta President Glen Hauenstein will announce the airline's

plan to apply at a news conference in Seattle, where the airline

is marking its inaugural nonstop flight to Taipei from the

United States.

If Delta is successful, it would compete with Alaska Airlines

, which operates the two current daily flights from

Seattle to Reagan.

"The addition of this flight will bring much-needed

competition to a route with some of the highest ticket prices in

the country," Delta said.

For more than a year, Delta heavily lobbied for the change -

and had pushed for adding far more daily flights - while United

Airlines opposed it.

Southwest Airlines ( LUV ) said it will apply for a new

daily flight between Washington and Las Vegas, which has only

one flight per day on American Airlines ( AAL ). Southwest ( LUV )

projects the flight would significantly lower average fares on

the route.

American Airlines ( AAL ) wants to start a new daily flight between

San Antonio and Washington, which would connect the

seventh-largest U.S. city to the DC airport.

Alaska Airlines is seeking a new daily flight to

Reagan from San Diego, the largest market without direct flights

to the DC airport, while Spirit Airlines ( SAVE ) wants a new

direct daily flight to San Jose, California.

Congress in 1966 said airplanes could only fly to

destinations within a 650-mile perimeter of National Airport,

with some exceptions, but decades later expanded the flight

distance to 1,250 miles. Since 2000, Congress has approved 25

daily flights beyond that range, including the five new ones.