Two crew chiefs from the 34th Aircraft Maintenance Unit, Ellsworth Air Force Base, S.D., complete a pre-flight checklist on a B-1B Lancer assigned to the 34th Bomb Squadron, Ellsworth AFB, during Green Flag-West 15-02 at Nellis AFB, Nev., Nov. 18, 2014. Green Flag-West provides combat training to joint and coalition warfighters in the art of air-land integration and the joint employment of airpower at the U.S. Army National Training Center at Fort Irwin, Calif. (U.S. Air Force photo by Staff Sgt. Siuta B. Ika)