A KC-135 Stratotanker sits on the flightline at McConnell Air Force Base, Kan., June 16, 2016. The KC-135 is the backbone of aerial refueling, and McConnell is the U.S. Air Force's premiere air refueling base with more Stratotankers than any other base. (U.S. Air Force photos/Airman 1st Class Josh Crawley)