Ellsworth Air Force Base, S.D., Airmen board a commercial aircraft prior to leaving for Green Flag, a training exercise hosted at Nellis Air Force Base, Nev., May 10, 2012. B-1 aircrews and Airmen in a wide variety of career fields are participating in the exercise now through May 24. (U.S. Air Force photo by Airman 1st Class Kate Thornton/Released)