U.S. Air Force Airman 1st Class Anthony Heise, 51st Maintenance Squadron tactical aircraft mechanic, performs maintenance on an F-16 Fighting Falcon aircraft in the Phase Hangar at Osan Air Base, Republic of Korea on Aug. 28, 2017. Between the G-force and constant vibrations, F-16s experience, they take a lot of abuse in the skies. Each jet must be fully examined in the Phase Hangar when crossing their 400 flight-hour milestones. (U.S. Air Force photo by Staff Sgt. Alex Fox Echols III)