A KC-135 Stratotanker departs from the flight line on Ellsworth Air Force Base, S.D., Sept. 10, 2019. The KC-135 is an aerial refueling aircraft – its primary fueling method utilizes the tanker’s boom. The boom is a long adjustable tube, which is controlled by a boom operator. The boom – situated toward the tail-end of the aircraft – is extended and inserted into the aircraft receiving fuel. (U.S. Air Force photo by Airman 1st Class Christina Bennett)