A crew chief from the 33rd Aircraft Maintenance Squadron, pulls chalks out from beneath an F-35A Lightning II July 6, 2017, at Eglin Air Force Base, Fla. The 33rd Fighter Wing sent 7 F-35As and more than 120 personnel to Nellis Air Force Base, Nev., for Exercise Red Flag 17-3. Red Flag is the Air Force's premier international air-to-air combat training exercise that provides a realistic environment to train a variety of domains: air, ground, space and cyberspace. (U.S. Air Force photo by Staff Sgt. Peter Thompson/Released)