The KC-135 Stratotanker, one of the oldest aircraft still flying in the US Air Force today, will likely get a life extension thanks to budget and replacement issues according to Gen. Carlton Everhart of Air Mobility Command, adding over 40 more years to its service record which began in the mid-1950s.
By the time this legendary aerial refueler enters retirement and is phased out from the USAF once and for all, it will have served just over 100 years — longer than any other aircraft in American history. Having seen action in virtually every American-involved conflict since 1956, the Stratotanker is easily one of the most recognizable and beloved aircraft flying today with the Air Force.
The KC-135 was, at first, supposed to be replaced entirely by the Boeing KC-46 Pegasus. But thanks to budget cuts and slashes to the projected buy for the KC-46, the Air Force will be left with a shortage of tankers to carry out aerial refueling operations both at home and overseas, severely impacting the service's ability to extend the range of the vast majority of its aircraft. Instead, the Air Force will be looking to upgrade its KC-135s into a "Super Stratotanker" of sorts, keeping it flying for 40 more years until the branch initiates the KC-Z replacement program to supersede the Stratotanker for good.
The KC-46, the result of the controversial KC-X program, was destined to be a larger longer-range follow-on to the KC-135, featuring two engines instead of four, and greater fuel carriage capacity, allowing for more aircraft to be refueling during a typical mission than what the Stratotanker could handle. However, the program has been constantly plagued with a variety of issues including cost overruns and delays, which ultimately led to the Air Force scaling down the number of Pegasus tankers it originally planned on buying to just 179.
This pushes retiring the KC-135 out of the question, as the Air Force (and Air National Guard) require a greater number of tankers to continue carrying out their mission at home and around the world.
While the USAF will continue with its plans to field the Pegasus, the Stratotanker fleet's life-extension seems inevitable. At the moment, the Air Force has already begun the $910 million Block 45 extension program, which seeks to keep these 60-year-old aircraft relevant and able to meet the needs of the modern Air Force. As part of the Block 45 updates, all American KC-135s will receive a new glass cockpit, replacing the older analog/gauge cockpits still in use, new avionics and an upgraded autopilot system, an enhanced navigation suite, and much more.
To keep the KC-135 flying for 40 more years, an advanced networking and electronic countermeasures suite would likely be the next upgrade the Air Force will pursue with the aircraft, during or after the completion of Block 45, which will end in 2028. Currently, the USAF estimates that their KC-135s have only used up around 35 percent of their lifetime flying hours, meaning that the aircraft is perfectly capable of flying on until 2040 with regular maintenance and scheduled overhauls.
As of 2014, there are 414 KC-135s in service with the US military — 167 assigned to the active duty Air Force, 180 to the Air National Guard, and 67 in the Air Force Reserve. Once the Air Force finishes procuring its 179 KC-46s, the number of Stratotankers in service will likely drop by 100 airframes, which will be retired to the boneyard at Davis Monthan AFB in Arizona.
It's also probable that the KC-135's current [younger] sister tanker, the three-engined KC-10 Extender, will receive a similar upgrade to keep its smaller fleet flying longer. Eventually, both of these aircraft will see their flying days come to an end with the initiation of the KC-Y and KC-Z next generation tanker programs, still decades away from coming to fruition.