KC-135 Stratotanker
ICAO K35RThe tanker that makes everything else possible, and one of the oldest airframes still in daily service. Live KC-135 positions and refuelling tracks.
Flying right now
Live · 30sAirframe
- Manufacturer
- Boeing
- Role
- Aerial refuelling
- Class
- L4J — Landplane, 4 jet engines
- Crew
- 3 — two pilots and a boom operator
- First flight
- 31 August 1956
- In service
- 1957
Operators airborne
About the KC-135 Stratotanker
Almost every long-range military flight you can watch on this site depends on a tanker somewhere, and most of the time that tanker is a KC-135. The design first flew in 1956 and the fleet is now approaching seventy years of continuous service.
Tankers are unusually rewarding to watch because their flight paths give the mission away. A KC-135 flying a long, slow racetrack at a fixed altitude is sitting on a published refuelling track waiting for receivers. Two tankers in the same orbit usually means something large is crossing.
The R model has CFM56 turbofans in place of the original water-injected engines — quieter, far more efficient, and the reason the type has stayed viable so long. The KC-46 is arriving to replace it, slowly.
Callsign prefixes
- ESSO
- A long-standing US tanker callsign block
- QUID
- Another common US Air Force tanker block
- PEARL
- Frequently seen on European-based tankers
- CTM
- Cotam — French C-135FR tankers
How to recognise it
- —A narrow, tube-like fuselage on a low swept wing — the airliner it shares ancestry with is the Boeing 707, not the 737.
- —The flying boom under the rear fuselage, with the boom operator's station just ahead of it.
- —On the feed, watch the track rather than the aircraft: sustained ovals at a constant altitude are a refuelling orbit.
Common questions
+ How old are the KC-135s still flying?
Most were built between 1957 and 1965. The airframes have been re-engined and repeatedly re-winged and re-skinned, but the basic structures are original, which makes this the oldest type routinely visible on ADS-B.
+ How can I tell a tanker is actually refuelling?
Look for two aircraft holding the same altitude, the same heading and near-identical ground speeds. A tanker flying a repeating oval at a constant level is on a refuelling track; when a receiver joins, both tracks converge and stay converged.
+ What is replacing the KC-135?
The Boeing KC-46 Pegasus, on a schedule that has slipped repeatedly. The KC-135 is expected to remain in service well into the 2040s alongside it.