Aircrews from the 37th Bomb Squadron perform pre-flight checks as a B-1 bomber thunders overhead during an Operational Readiness Exercise on Ellsworth Air Force Base, S.D., Feb. 23, 2012. B-1B missions were conducted during the ORE that tested the base’s ability to rapidly mobilize and process assets during wartime contingencies. (U.S. Air Force photo by Airman 1st Class Zachary Hada/Released)