An F-16 Fighting Falcon assigned to the 121st Fighter Squadron, District of Columbia Air National Guard, takes off from Eielson Air Force Base, Alaska, May 5, 2015, during RED FLAG-Alaska 15-2. (Joshua Turner/U.S. Air Force)

Staff Sgt. Michael Misiewicz, a C-5M Super Galaxy crew chief, visually inspects wheel-speed transducer wiring inside a main landing gear axle of a C-5M during a tire change and brake replacement on April 29, 2015, at Dover Air Force Base, Del. (Greg L. Davis/U.S. Air Force)

F-16 Fighting Falcons from the 18th Aggressor Squadron at Eielson Air Force Base, Alaska, refuel behind a KC-135 Stratotanker assigned to the Pennsylvania Air National Guard's 171st Air Refueling Wing, while flying over the Joint Pacific Alaska Range Complex on May 11, 2015, during Red Flag-Alaska 15-2. (Shawn Nickel/U.S. Air Force)

Senior Airman Tiffany Hamilton, 455th Expeditionary Medical Operations Squadron medical technician, and Lt. Col. Paul Cory, 817th Expeditionary Air Support Operations Squadron commander, practice Krav Maga techniques during a bi-weekly class at Bagram Air Field, Afghanistan, May 7, 2015. (Joseph Swafford//U.S. Air Force)

A Portuguese air force EH-101 Merlin helicopter hovers near a simulated accident site during a joint exercise on Terceira, Azores, Portugal, on May 6, 2015. (Zachary Wolf/U.S. Air Force)

An F-16 Fighting Falcon assigned to the 13th Fighter Squadron at Misawa Air Base, Japan, launches for a training sortie on May 6, 2015, during Red Flag-Alaska 15-2 at Eielson Air Force Base, Alaska. (Peter Reft/U.S. Air Force)