WASHINGTON (Reuters) - Delta Air Lines 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 said it will apply for a new daily flight between Washington and Las Vegas, which has only one flight per day on American Airlines. Southwest projects the flight would significantly lower average fares on the route.

American Airlines 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 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.