American refueling aircraft, deployed during Cold War, Desert Storm and ongoing operations worldwide for mid-air refueling missions. Key figures: top speed 933 km/h, range 17,727 km, service ceiling 15,240 m, max takeoff weight 146,283 kg, unit price $39M, built 803. In service with 3 air forces as of 2026 — United States (374), Turkey (7), Chile (3).
| Crew | 4 |
| Length | 41.5 m (136.3 ft) |
| Wingspan | 39.9 m (130.8 ft) |
| Height | 12.7 m (41.7 ft) |
| Wing area | 226 m² (2432.6 sqft) |
| Empty weight | 44,663 kg (98,465 lbs) |
| Max. takeoff weight | 146,283 kg (322,498 lbs) |
| Powerplant | 4 × turbofans CFM International F108-CF-100 9,813 kgf each |
| Maximum speed | 933 km/h (580 mph) |
| Operational range | 17,727 km (11,015 mi) |
| Endurance | 11 hours |
| Service ceiling | 15,240 m (50,000 ft) |
| Climb rate | 24.893 m/s (81.7 ft/s) |
United States
Two KC-135R tankers damaged in a ground towing accident at RAF Mildenhall; one tanker's stabilizer struck the adjacent aircraft's, leaving tearing and deformation. Repaired on the ramp within days; no injuries.
Damaged
United States
KC-135R Stratotanker destroyed by fire at Prince Sultan Air Base during Iranian missile and drone attack; satellite imagery confirmed airframe loss.
Destroyed
United States
Five KC-135R/T Stratotankers damaged by Iranian ballistic missile strike on Prince Sultan Air Base flight line; none destroyed, all expected to return to service.
Damaged
United States
Second KC-135 in the western Iraq mid-air collision lost part of its vertical stabilizer; landed safely at Ben Gurion.
Damaged
United States
KC-135R Stratotanker crashed in western Iraq near Turaibil after mid-air collision with another KC-135 during Operation Epic Fury; 6 crew aboard killed.
Crash
The Boeing KC-135 Stratotanker is a four-engined aerial refuelling aircraft operated by the United States Air Force since 1957. Derived from the Boeing 367-80 demonstrator alongside the 707 airliner, it was the USAF's first jet tanker, replacing the piston-engined KC-97 Stratofreighter, and has refuelled American bombers and fighters in every major campaign from Vietnam to the 2026 war with Iran. Some 375 remain in USAF service as of mid-2026, flown by active-duty, Air Force Reserve and Air National Guard units, while the Boeing KC-46A Pegasus gradually takes over the mission.
Strategic Air Command's KC-97 carried gasoline for its own piston engines and kerosene for its receivers, and its 230 mph (370 km/h) cruise forced jet bombers almost to the stall to take fuel. Boeing offered a tanker version of its privately funded Model 367-80 "Dash 80" jet transport, flown in 1954. SAC's 1954 competition went in 1955 to Lockheed's L-193 design, but because the Boeing aircraft was already flying and could be delivered two years earlier the Air Force ordered it as an interim type, then dropped the Lockheed order rather than support two tankers.
The initial order covered 29 KC-135As. The first flew on 31 August 1956 and the first operational Stratotanker reached Castle AFB, California, in June 1957. Production of 732 KC-135As ended in 1965, within a C-135 family of some 820 airframes. Despite the resemblance, the KC-135 predates the 707 and shares little structure with it.
The KC-135 has 35-degree swept wings and tail and four engines in underwing pods. It is 136 ft 3 in (41.53 m) long with a span of 130 ft 10 in (39.88 m) and a maximum takeoff weight of 322,500 lb (146,300 kg). The KC-135R's four CFM International F108-CF-100 (CFM56) turbofans deliver 21,600 lbf (96 kN) each, for a maximum speed of 504 kn (933 km/h), a 50,000 ft (15,000 m) ceiling and a radius of 1,300 nmi (2,400 km) with 150,000 lb (68,000 kg) of transferable fuel out of a 200,000 lb (90,700 kg) capacity.
Nearly all of that fuel can be passed through the tail-mounted flying boom, flown by a boom operator from a prone station under the tail. Probe-equipped receivers are served either by a shuttlecock drogue fitted to the boom tip before flight (the boom drogue adapter, which rules out boom receivers on the same sortie) or by the Multi-Point Refueling System's Mk 32B hose-and-drogue wing pods, which let two Navy, Marine Corps or NATO jets take fuel at once while the boom stays available. A cargo deck above the tanks carries up to 83,000 lb (38,000 kg) of freight or 80 passengers. The basic crew is pilot, co-pilot and boom operator.
Every KC-135 was built with Pratt & Whitney J57 turbojets of 10,000 lbf (44 kN), about 13,000 lbf (58 kN) with water injection on takeoff. Two re-engining programmes transformed the fleet. In the 1980s about 160 Reserve and Guard aircraft received TF33 turbofans salvaged from retired 707 airliners, becoming KC-135Es. The larger programme fitted the CFM56, designated F108 in USAF service, to more than 400 KC-135As and some Es (KC-135R) and to 54 KC-135Qs (KC-135T). The F108 nearly doubles the J57's thrust, allows 50 percent more fuel to be offloaded on a long sortie, cuts fuel burn and operating cost by about a quarter and lowers takeoff noise by 27 decibels.
Avionics followed. Pacer-CRAG (compass, radar and GPS), applied fleet-wide from 1999 to 2002, replaced the fuel-management system and removed the navigator from the standard crew. Block 45, with the first 45 aircraft delivered by January 2017, replaces the no-longer-procurable analogue instruments with a glass cockpit, digital autopilot and flight director and a new radio altimeter.
The RC-135 Rivet Joint, EC-135 Looking Glass, OC-135 Open Skies and NASA's NKC-135 test beds share the C-135 airframe but are separate types, not tanker variants.
The KC-135 was bought to extend the reach of SAC's B-47 and B-52 bombers, and until 1992 it belonged to SAC, joined by Guard and Reserve units from 1975. In Southeast Asia from the mid-1960s its role widened: tankers let F-105 and F-4 fighter-bombers spend hours rather than minutes over the target, fed B-52 missions and nursed battle-damaged aircraft with punctured tanks back to friendly fields, switching to the drogue adapter for Navy and Marine Corps jets.
Stratotankers supported the 1991 Desert Storm air campaign in large numbers. When SAC was inactivated in 1992 most KC-135s passed to the new Air Mobility Command, with smaller detachments under USAFE, PACAF and the training command. In May 2018 AMC managed 396 Stratotankers, 243 of them Reserve and Guard aircraft. Through Allied Force, Enduring Freedom, Iraqi Freedom and Inherent Resolve it remained the backbone of the tanker orbits over the Balkans, Afghanistan, Iraq and Syria. The oldest aircraft flying in the US military is a 1957-built KC-135 of the Arizona Guard's 161st Air Refueling Wing.
More than 30 KC-135s and KC-46s deployed to Israel before the US-Israeli campaign against Iran opened on 28 February 2026, and the type sustained the bomber and fighter strikes that followed. The war cost the fleet its first loss since 2013: on 12 March two KC-135Rs collided in mid-air over western Iraq, near the Jordanian border, during a refuelling sortie. One crashed, killing all six crew, three of them from the Ohio Air National Guard's 121st Air Refueling Wing; the other lost the upper part of its vertical stabiliser but reached Ben Gurion Airport in Israel and was later flown to Tinker AFB for repair. US Central Command said the collision was not caused by hostile or friendly fire. On the ground, an Iranian ballistic missile strike on Prince Sultan Air Base in Saudi Arabia on 13 March damaged five KC-135s parked on the flight line, all repairable, and a further missile and drone attack on the base on 27 March set a KC-135R on fire and destroyed it, damaging others nearby. A ceasefire in April 2026 ended the strikes.
The USAF flies 375 KC-135s as of June 2026 — 157 with active-duty wings, 62 with the Air Force Reserve and 156 with the Air National Guard. Turkey operates seven KC-135Rs and Chile a handful of former USAF KC-135Es received from 2010. France took delivery of twelve new-build C-135Fs in 1964, re-engined eleven with F108s as C-135FRs in 1985–88 and retired the last in December 2023 in favour of the A330 MRTT Phénix; Singapore flew four ex-USAF KC-135Rs from 1999 to 2019, also replaced by A330 MRTTs. Both retired fleets went to the US contractor Metrea, which bought the Singapore aircraft in 2020 and the French ones in June 2024 and operates some 15 KC-135Rs under contract, one of them wet-leased to India since November 2025 for tanker training.
More than 50 Stratotankers have been lost in accidents over the type's career, most in the J57 era: takeoff crashes, mid-air collisions with receivers such as the 1966 Palomares B-52, and fuel-pump explosions that led to a rule keeping 3,000 lb (1,400 kg) of fuel in the affected tanks. The last fatal loss before the 2026 collision was a KC-135R that broke up after takeoff from Manas, Kyrgyzstan, on 3 May 2013 when a rudder control malfunction induced an unrecognised Dutch roll, killing its three crew.
Depot workload doubled and overhaul costs tripled between 1993 and 2003, though a 2005 study still put the R-standard aircraft's useful life at 2030. A 2003 deal to buy 80 and lease 20 Boeing KC-767s was frozen amid a procurement scandal and cancelled in January 2006. The KC-X competition launched in January 2007 chose the Northrop Grumman/EADS KC-45 in February 2008, a decision overturned on Boeing's protest; a rerun selected Boeing's 767-based KC-46A Pegasus in February 2011, and the first was delivered in January 2019. The KC-135 will leave service gradually as KC-46A units stand up.
The first Boeing KC-135A flew on August 31, 1956. Seventy years on, 385 Stratotankers remain in service with three air forces, 52 percent of the world's 740 dedicated tankers, and 2026 has already cost the fleet two airframes and damaged eight more.
