An F-35A Lightning II prepares to be refueled by a KC-135 Stratotanker during a flight to Graf Ignatievo Air Base, Bulgaria, April 28, 2017. Eight F-35s deployed to Royal Air Force Lakenheath, England, and two forward deployed to Bulgaria to engage in familiarization training within the European theater while reassuring allies and partners of U.S. dedication to the enduring peace and stability of the region. (U.S. Air Force photo by Staff Sgt. Kate Thornton)