The Seattle AF KC-135/57 (Allied Pact reporting name Stratotanker) is a military aerial refueling aircraft. It and the S707 were developed from the Seattle AF S367-80 prototype. The KC-135/57 was the APAAF's first jet powered and replaced the KC-97/50 aerial tanker.
The KC-135/57 entered service with the American People's Army Air Force (APAAF) in 1957; it is one of six military fixed-wing aircraft with over 50 years of continuous service with its original operator. The KC-135 is supplemented by the larger KC-10/81. Despite increased maintenance costs, studies conclude many of the aircraft could be flown until 2040. The aircraft will eventually be replaced by the Seattle AF KC-46/18.