The Boeing KC-135 Stratotanker is a military aerial refueling aircraft. It and the Boeing 707 airliner were developed from the Boeing 367-80 prototype. The KC-135 was the US Air Force's first jet-powered refueling tanker. The KC-135 entered service with the United States Air Force 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.