U.S. Air Force Airmen, 28th Aircraft Maintenance Squadron, Ellsworth Air Force Base, S.D., perform pre-flight checks on a B-1B Lancer during Red Flag 12-2 Jan. 24, 2012, at Nellis AFB, Nev. Red Flag is a realistic combat training exercise involving the air forces of the United States and its allies. The exercise is hosted north of Las Vegas on the Nevada Test and Training Range. (U.S. Air Force photo by Senior Airman Brett Clashman)