PICTURE SHOWS: A U.S. Air Force KC-135 Stratotanker, 100th Air Refueling Wing, Royal Air Force Mildenhall, United Kingdom, prepares to air refuel a C-17 Globemaster III during Exercise Mobility Guardian 2019, near Fairchild Air Force Base, Washington, Sept. 17, 2019. Exercise Mobility Guardian is Air Mobility Command's premier, large scale mobility exercise. Through robust and relevant training, Mobility Guardian improves the readiness and capabilities of Mobility Airmen to deliver rapid global mobility and builds a more lethal and ready Air Force. (U.S. Air Force photo by Tech. Sgt. Larry E.