Three additional B-1B Lancer bombers arrived at RAF Fairford in the United Kingdom on March 26, bringing the total number of bombers at the base to 21, one of the largest U.S. bomber deployments in recent history.

Axar.az reports, citing Air and Space Force Magazine, according to local spotters, air traffic control communications, and flight-tracking data, the base now hosts 15 B-1B and six B-52H aircraft, with the 15 B-1Bs representing roughly a third of the Lancer fleet still in service.

The U.K. has confirmed that Fairford is being used to support U.S. operations targeting Iranian missile facilities, part of Operation Epic Fury, which began February 28.

The B-1Bs, capable of carrying large internal payloads of guided bombs, are among the most heavily deployed bombers, while the B-52s have been used to strike Iranian targets with standoff missiles. CENTCOM sources have said that the vast majority of missions use “stand-in” munitions.