U.S. Air Force Capt. Kevin LeRoux, 351st Air Refueling Squadron pilot, reviews a pre-flight checklist prior to a flight supporting exercise Joint Warrior 19-1 at RAF Mildenhall, England, April 4, 2019. Exercise Joint Warrior is a biannual, U.K.-led multinational exercise and one of largest NATO exercises in Europe, involving 13 countries. (U.S. Air Force photo by Tech. Sgt. Emerson Nuñez)