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 and replaced the KC-97 Stratotanker. The KC-135 was initially tasked to refuel strategic bombers, but was used extensively in the Vietnam War and later conflicts such as Operation Desert Storm to extend the range and endurance of US tactical fighters and bombers.
The KC-135 entered service with the United States Air Force (USAF) 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. Despite increased maintenance costs, studies conclude many of the aircraft could be flown until 2040. The aircraft will eventually be replaced by the Boeing KC-46 Pegasus.
Like its sibling, the commercial Boeing 707 jet airliner, the KC-135 was derived from the Boeing 367-80 jet transport “proof of concept” demonstrator, which was commonly called the “Dash-80”. The KC-135 is similar in appearance to the 707, but has a narrower fuselage and is shorter than the 707. The KC-135 predates the 707, and is structurally quite different from the civilian airliner. Boeing gave the future KC-135 tanker the initial designation Model 717.
In 1954 USAF‘s Strategic Air Command (SAC) held a competition for a jet-powered aerial refuelling tanker. Lockheed’s tanker version of the proposed Lockheed L-193 airliner with tail-mounted engines was declared the winner in 1955. Since Boeing’s proposal was already flying, the KC-135 could be delivered two years earlier and Air Force Secretary Harold E. Talbott ordered 250 KC-135 tankers until the Lockheed’s design could be manufactured. In the end, orders for the Lockheed tanker were dropped rather than supporting two tanker designs. Lockheed never produced its jet airliner, while Boeing would eventually dominate the market with a family of airliners based on the 707.
In 1954 the Air Force placed an initial order for 29 KC-135As, the first of an eventual 820 of all variants of the basic C-135 family. The first aircraft flew in August 1956 and the initial production Stratotanker was delivered to Castle Air Force Base, California, in June 1957. The last KC-135 was delivered to the Air Force in 1965.
Reconnaissance and command post variants of the aircraft, including the RC-135 Rivet Joint and EC-135 Looking Glass aircraft were operated by SAC from 1963 through 1992, when they were reassigned to the Air Combat Command (ACC). The USAF EC-135 Looking Glass was subsequently replaced in its role by the U.S. Navy E-6 Mercury aircraft, a new build airframe based on the Boeing 707-320B.