B-1 bomber crews start engines prior to takeoff for the Global Strike Challenge at Ellsworth Air Force Base, S.D., Sept. 18, 2014. The challenge gives Ellsworth a chance to showcase the capabilities of their B-1 bombers and crews, earning points for how close the bomb was placed to the target, how accurately the bomb was timed to drop and how well the teams communicated with each other. (U.S. Air Force photo by Airman 1st Class Rebecca Imwalle/Released)