A B-52 Stratofortress approaches a KC-135 Stratotanker for an aerial refueling training mission, Sept. 2, 2015, over Kansas. The KC-135 has been providing American and allied forces aerial refueling capabilities since the 1950s and played a major role in the deterrence of the Soviet Union during the Cold War. (U.S. Air Force photo by Airman Jenna Caldwell.)