Group : Tanker Aircrafts
Status : Active
Also Known As : C-135 Stratolifter, C-135C Speckled Trout, C-135F, C-135FR, EC-135, EC-135C, EC-135E, KC-135A, KC-135E, KC-135Q, KC-135R, KC-135T, NC-135E Big Crow (test aircraft), NKC-135, NKC-135A, OC-135, RC-135, RC-135S Cobra Ball, RC-135U, RC-135V Rivet Joint, RC-135W, TC-135W, WC-135M
Origin : United States of America
Contractor : Boeing
Initial Operational Capability (IOC) : June 1957
Total Production : 732
Unitary Cost : USD $40 million

The KC-135 Stratotanker is a tanker aircraft designed to provide refueling for US Air Force, US Navy and USMC aircraft, as well as aircraft from allied nations. The first KC-135 tanker was delivered to the Castle US Air Force Base, California, in June 1957 and the last one in 1965. The KC-135 has an aerial boom as primary fuel transfer method. A special shuttlecock-shaped drogue, attached to and trailing behind the flying boom, may be used to refuel aircraft fitted with probes. In addition, the KC-135 can accommodate passengers and cargo (up to 83,000 pounds) in a deck above the refueling system.

As of 2006, the US Air Force's inventory includes 417 KC-135Rs and 112 KC-135Es. The number of E models would drop to 63 aircraft by fiscal year 2011. The future of KC-135 fleet remains uncertain due to a corrosion problem that would escalate into maintenance costs growth. The KC-X tanker replacement program envisages that the last Stratotanker should be retired from the fleet by 2040.

Boeing is offering its KC-767 tanker aircraft as replacement for aging KC-135 tankers, while Northrop-Grumman/EADS North America are offering the Airbus A330 MRTT. The deals are on hold pending law suit and further US Air Force and governmental studies. Both tankers will be evaluated by the USAF under the KC-X program. The C-135C Speckled Trout was a variant introduced in the mid 1970s as a VIP transport for the US Air Force chief of staff. This aircraft was retired in early February 2006.