USAF KC-10 Extender tanker aircraft farewell repeats B-52 Stratofortress bomber paradox

I became interested in military aviation when I was a child reading the "Aviones de Guerra" (War Planes) collection, launched in Spain in 1987.

The USAF shows more photos of the B-21 Raider and talks about a future without B-1B nor B-2
A report that shows how a Boeing B-52 Stratofortress strategic bomber works

Those fascicles were my favourite reading for years, to the point where I knew by heart the exact dimensions and performance of the main fighter aircraft of the time. The Boeing KC-135 tanker was already a veteran of the United States Air Force (USAF) at that time, having been in service for 30 years (it made its first flight in 1956 and entered service in 1957).

Advantages of the KC-10 over the KC-135

In the field of aerial refueling aircraft, the big novelty at that time was the McDonnell Douglas KC-10 Extender, based on the three-engine DC-10 commercial airliner. The Extender had made its first flight in 1980 and entered service in 1981. It was a larger aircraft with greater cargo capacity than the KC-135, and had the advantage of being able to refuel by the boom system (used by USAF aircraft) and also by the hose and bucket system (used by the US Navy and Marines).

The KC-10 was vastly superior to the KC-135 in other respects. It had almost twice the fuel carrying capacity (375,000 lb (165,561 kg) versus its predecessor’s 200,000 lb (90,718 kg). It could also carry more than twice the load (170,000 lb (77,110 kg) versus 80,000 lb (38,000 kg). In addition, its refueling system was digitalized. The KC-10 was a large strategic refueling aircraft, having a range of over 4,300 miles (7,000 km) fully loaded versus the KC-135’s 1,500 miles (2,400 km).

Farewell to the last KC-10 in active service in the USAF

I'm talking about the Extender in the past tense because the KC-10 is history: On September 26, the USAF said goodbye to the last of these active aircraft, 79-1948, in a ceremony held at Travis AFB, California. That day, that KC-10 made its final flight to AMARG, the massive aircraft graveyard at Davis-Monthan AFB in Arizona, where these planes will be available should they ever need to return to service.

The USAF still has 10 active KC-135 squadrons

The DC-10 is being replaced by the Boeing KC-46 Pegasus, the military in-flight refueling version of the Boeing 767 commercial aircraft. What I never imagined as a child is that at 48 years old I would see something unusual: after the KC-10's farewell, 10 KC-135 squadrons are still active in the USAF, according to "The Military Balance 2024" by the International Institute for Strategic Studies. The USAF has decommissioned a 43-year-old aircraft and is keeping an aircraft that has been in service for 67 years.

How can this be explained? First, it is due to the large number of Stratotankers. 803 KC-135s were built, of which 376 are still in service, including aircraft serving in the Air National Guard (ANG) and the Air Force Reserve (AFRES). Those active KC-135s number 325 KC-135Rs (average age 61.71 years) and 51 KC-135Ts (average age 63.73 years). This is a huge fleet, and one that was not intended to be replaced by the Extender. In fact, 60 KC-10s were built and at the beginning of this year 21 were still in service (there are none left even in the ANG and AFRES). The average age of these last KC-10s was 38.61 years. There are currently 72 KC-46s in service.

A paradox similar to that of the B-52 bomber

The KC-135 is a paradox like that of the Boeing B-52 Stratofortress bomber, which made its first flight in 1952 and entered service in 1955. It has been years since the entry into service of two more modern bombers, the B-1B Lancer (supersonic and in operation since 1986) and B-2 Spirit (with stealth capability and in operation since 1997). However, following the unveiling of the B-21 Raider, in December 2022 the USAF published its forecast for retiring the B-1B and B-2, while contemplating a "future Air Force bomber force consisting of B-21s and B-52s". This is largely explained by the lower operating cost of the B-52 compared to the B-1B and B-2.

The situation is similar with tankers. According to 2009 data, the KC-10's flight cost per hour was more than twice that of the KC-135. Admittedly, some excellent aircraft were made during the Cold War, and they are proving their worth many years after the most optimistic forecasts for them when they entered service. Long live the KC-135!

---

Main photo: U.S. Air Force. A KC-10 Extender from the 76th Air Refueling Squadron takes off over the Atlantic Ocean on February 14, 2018.