U.S. Air Force 1st Lt. James Herbert, 351st Air Refueling Squadron, performs pre-flight checks during exercise Astral Knight at RAF Mildenhall, England, June 3, 2019. AK19 is a joint, multinational exercise which aims to demonstrate the integration, coordination, and interoperability of joint existing command and control at the operation and tactical levels. (U.S. Air Force photo by Airman 1st Class Brandon Esau)