Airman 1st Class Jeremy Hamilton, 92nd Aircraft Maintenance Squadron crew chief, gives the “normal stop” hand signal to a KC-135 Stratotanker preparing to taxi down to the runway Sept. 9, 2015, at Fairchild Air Force Base, Wash. Crew chiefs, or aerospace maintenance technicians, perform scheduled inspections, maintain and repair many parts of an aircraft and are responsible for ensuring the aircraft is operational. (U.S. Air Force photo/Airman 1st Class Mackenzie Richardson)