Virginia Air National Guard Master Sgt. Russell Tilley, 192nd Maintenance Squadron aerospace propulsion technician, checks wires for possible damage during a pre-test inspection on an F-22 Raptor engine at Langley Air Force Base, Va., July 22, 2015. Propulsion technicians conduct tests to ensure the engine is working properly. (U.S. Air Force photo by Airman 1st Class Derek Seifert/Released)