Staff Sgt. Mark Duque, 28th Aircraft Maintenance Squadron B-1 bomber crew chief, reviews aircraft maintenance procedures during a pre-flight inspection at Ellsworth Air Force Base, S.D., Sept. 10, 2013. Crew chiefs use technical data to diagnose and solve maintenance problems on aircraft systems and interpret procedures and policies to repair aircraft and related equipment. (U.S. Air Force photo by Airman 1st Class Zachary Hada/Released)