Undoubtedly the most important aircraft of its kind ever produced, the Boeing KC-135 Stratotanker has been the mainstay of the USAF's tanker fleet ever since it was introduced as early as the 1960s for service with the Strategic Air Command. The KC-135 is based on the Boeing 367-80 (on which the 707 airliner was based upon) with minimal external differences other than a prominent flying boom in the rear fuselage, its principal means of inflight-refuelling although it can also use a shuttlecock-shaped drogue for aircraft fitted with probes. Entering service before the Vietnam War, the KC-135 revolutionized air warfare by allowing aircraft to operate far beyond their original range, an inmense advantage to the USAF's global committments. Such is the success that hundreds of KC-135s remain in active and reserve service in the United States as well as having been exported to a number of countries, most notably France which has 11 units in service.

Built from the Boeing 367-80 (and not the 707 as commonly believed), the initial KC-135A flew for the first time in August 1956 with deliveries beginning the following year. Production of over 700 units took less than a decade and they have been continually upgraded over the years, initially into the KC-135E with new engines, brakes and a number of fuselage parts from 707s like tail units, engine pylons and cowlings. A more recent upgrade resulted in the KC-135R, also with a new engine but also with improved hydraulic and pneumatic systems as well as modern avionics and the ability to operate from shorter civil airfields. The basic 367-80 (known as the C-135 Stratolifter in military service) has also led to a number of additional variants including the RC-135 electronic intelligence aircraft, the OC-135 for observation flights in support of the Open Skies Treaty, the EC-135 communicasions relay aircraft (some featuring a pronounced bulbous nose for tracking missiles and spacecraft) and finally, the WC-135 Constant Phoenix atmospheric collector for detection of nuclear explosions.