WASHINGTON, Oct 16 (Reuters) -

The U.S. Transportation Department on Wednesday said it was

tentatively awarding five new daily round trip flights from

Washington Reagan National airport to major airlines.

The flights at the busy airport in Arlington, Virginia,

outside the nation's capital were mandated under legislation

signed in May by President Joe Biden.

American Airlines ( AAL ), Delta Air Lines ( DAL ), United

Airlines Southwest Airlines and Alaska Airlines

are all receiving tentative new flights. The

Transportation Department issued a "show cause" order that will

allow for public comment or objections for two weeks and

responses for one week before final orders on the slots are

issued.

The law requires the Transportation Department to select

the flights to expand service to cities without direct service

and to boost competition in markets with existing service.

The Washington region has three major airports, but

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

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

the U.S., and Reagan is the 24th-busiest U.S. airport by

passengers.

The airlines did not immediately comment.

The flights chosen include a new Delta flight to

Seattle, a new Southwest Las Vegas flight and a new American

Airlines ( AAL ) daily flight between San Antonio and Washington, which

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

Alaska Airlines tentatively received a new daily flight

to Reagan from San Diego, the largest market without direct

flights to the DC airport, while United Airlines has tentatively

won a new flight to San Francisco.

The Transportation Department rejected a proposal by

JetBlue ( JBLU ) to add a flight to Puerto Rico from Washington.

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, including the five new ones.

The fight over the new flights was a key reason an

aviation reform bill was

delayed for more than six months

.