A crew chief, 148th Fighter Wing, Duluth, Minn. prepares a Block 50, F-16 for take-off during a Sentry Savannah training exercise, Feb 10, 2015, Savannah, Ga. The Sentry Savannah training exercise allows fighter pilots to participate in war simulations that depict what they would face in a real world scenario. (U.S. Air National Guard photo by Master Sgt. Ralph Kapustka/Released)