South Korea said it had conducted a joint drill with a U.S. supersonic B-1B Lancer bomber on Monday.

The B-1B Lancer bombers and F-15 fighter escorts were in international airspace over waters east of North Korea.

Airmen of the 28th Maintenance Squadron prepare a B-1B Lancer to support Operation Odyssey Dawn on Ellsworth Air Force Base, S.D., March 27, 2011.