U.S. Air Force Senior Airman Jacob O'Brien, a 148th Fighter Wing crew chief, Duluth, Minn., goes through pre-flight checks with an F-16 pilot, Aug. 10, 2015, while participating in RED FLAG-Alaska 15-3 at Eielson Air Force Base, Alaska. RF-A is a Pacific Air Forces commander-directed field training exercise for U.S. and partner nation forces, providing combined offensive counter-air, interdiction, close air support and large force employment training in a simulated combat environment. (U.S. Air Force photo by Master Sgt. Ralph Kapustka/Released)