The Case for a Three-Tanker Air Force


The U.S. Air Force is about to execute a plan that could have irreversible consequences, and time is running out to change course. Before it retires the KC-10 “Extender,” its long-distance, high-capacity aerial refueling plane, the Air Force should reconsider. America’s return to great power conflict requires a force that can reach China and Russia from far-away U.S. air bases. Whether the Air Force is moving a large number of fighters, transporting cargo and personnel, or refueling long-range bombers, a long-range, large-capacity airplane is required. The Extender remains the best platform to refuel those strategically vital flights.

America’s strategic focus has shifted from containing terrorist groups like ISIS to competing with rising great powers. The ability of countries like China and Russia to contest U.S. efforts in multiple domains will limit America’s basing options. This will demand the types of advanced warfighting planes that can’t reach distant targets from America’s shores without air refueling. Deterrence today requires reach, which requires volume. The current plan to replace the heavy tanker with a fleet of smaller-capacity ones creates an unnecessary vulnerability. Policymakers should seriously consider funding and keeping the KC-10. The problem is urgent because the United States is quickly running out of time to act to preserve this capability. If there is any appetite to keep this aircraft flying, now is the time to articulate that decision and act on it. Once the Air Force uproots simulators and turns off training pipelines, it will be past the point to actually salvage an airplane that is strategically necessary.



The U.S. Air Force is fast approaching the most significant change in the composition of its air refueling tanker force since the late 1970s. The first KC-46 “Pegasus,” which is the most technically advanced tanker in the world, was delivered in January of this year, and more continue to arrive off the production line. As they undergo testing and evaluation to become operationally capable, aircrews will soon begin flying the middle-aged fleet of 59 KC-10s to the boneyard. The plan to retire the KC-10 was developed at the height of sequestration based on fiscal policy, not strategic necessity. Taken together, these unconnected but simultaneous events will fundamentally reshape the Air Force’s refueling capability.

Given the changes in America’s strategic posture, new fiscal realities, the rise in great power competition, and a renewed focus on military readiness, there is ample justification to reconsider this plan. It is time for a serious reexamination of the budget-driven decision to retire the KC-10, and there is a path to do this that allows the Air Force to best preserve its vital air refueling capabilities in the face of rising costs and a changing geo-political landscape. We will argue that retiring the KC-10 may save dollars, but it does not make sense. America’s interests are best served by a three-tanker Air Force for the foreseeable future.

Tankers 101

The Air Force tanker inventory is made up of KC-135s, KC-10s, and, as of January 2019, KC-46s. Several differences between the planes are noteworthy, including age, size, cost-per-hour to operate, and offload capability (the amount of gas each tanker can offload to other airborne aircraft). KC-135 “Stratotankers” are Boeing 707 airframes and have been in service since the 1950s. With a basic crew of two pilots and a boom operator, they are the workhorse of the tanker fleet. KC-10s are modified DC-10s, in service since 1980 and dubbed the “Extender” because of their massive offload capability. The KC-46s are modified Boeing 767s fresh off the production line. This aircraft will bring new capabilities such as airborne defensive systems to the tanker community, but they can only offload a little more than the Stratotanker and have been mired in delays and technical problems costing Boeing over $3 billion.

The basic statistics of each airframe are as follows:

Airframe Total Current Inventory Began Service Fuel Use per Hour Price per/hr of Operation Weight (short tons) Number of Passengers Max Fuel Load (lbs) Capable of Onloading Fuel Defensive Systems
KC-135 “Stratotanker” 396 1956 11,142 $19,000 18 53 200,000 No*** No
KC-10 “Extender” 59 1980 18,099 $21,000 85 75 356,000 Yes No
KC-46 “Pegasus” 19* 2019 11,500 Unknown 32.5** 58** 210,000 Yes Yes

* Number projected to grow by 3 jets/month for 2019 and 179 total in future years

** The KC-46 is currently prohibited from carrying any passengers or cargo.

*** A small number of KC-135s are capable of onloading fuel. These are primarily used for special operations missions

The Pegasus will be a phenomenal platform with capabilities and defensive systems that no Air Force tanker has ever had. However, in terms of volume, it carries far less fuel than the KC-10 because it was designed to replace the older KC-135 under the original but now-defunct plan to upgrade the aging Air Force tanker fleet.

The Divestment Plan

The Air Force will soon retire the KC-10 as the KC-46 comes on-line over the next several years. The current plan is to transition from a fleet of 455 tankers consisting of 396 KC-135s and 59 KC-10s, to a fleet of 479 tankers made up of 300 KC-135s and 179 KC-46s. The transition began this fiscal year and is scheduled to finish in the late 2020s. As part of the plan, all eight of the current Extender squadrons at Joint Base McGuire-Dix-Lakehurst and Travis Air Force Base will transition to flying the Pegasus, leaving the Air Force without a large tanker in its inventory.

This current divestment plan is flawed for two reasons. First, it would be the only instance in Air Force history where a major weapon system is retired and replaced by one that is less capable in its primary mission: air refueling. Second, the plan calls for flying some Stratotankers until they are 100 years old. Even with new engines, modern glass cockpits, and excellent maintenance, most large airframes were not structurally designed to fly for a century. Additionally, this plan runs counter to recent strategic-level guidance such as the National Security Strategy, which states that “the United States must reverse recent decisions to reduce the size of the Joint Force and grow the force while modernizing and ensuring readiness.” Rather than trading the capability to offload large amounts of fuel for a technologically advanced platform, the Air Force should return to a modified version of its original plan to gradually retire the older Stratotanker to make way for the new tanker.

A Changing Fiscal and Strategic Landscape

Money ultimately drove the decision to retire the KC-10 early. During the height of sequestration there was intense pressure on the Department of Defense to make significant budgetary cuts, and the Air Force was forced to make some difficult decisions. Because there is only a small fleet of KC-10s, it is relatively expensive to operate considering flying hour and maintenance costs per aircraft. Eliminating an entire logistics supply chain for an airframe offers a significant cost savings. Early retirement created budgetary space by saving billions vs. millions. That allowed the Air Force to keep programs like the KC-46 and F-35 on track.

However, things have changed significantly since 2013. The Air Force is no longer under the acute fiscal pressure of sequestration. Although sequestration is technically still in effect, Congress and the President are executing a substantial revitalization of U.S. military assets. In addition, there has been an aggressive focus on military readiness since 2017 due to the changes in the geo-political environment. Both the National Security Strategy and the National Defense Strategy identify great power competition, not violent extremism, as our biggest national security threat. Additionally, America continues to face challenges from smaller powers like Iran and North Korea, whose respective abilities to operate just below the threshold of open hostility continue to shape our military requirements. In light of these broad changes, let’s consider what capabilities the United States is about to lose.

Why Keep the KC-10?

The KC-10, known as ‘Big Sexy’ by many aircrews, is a workhorse platform that brings several distinctive capabilities to the joint warfighter. Among these are:

High-Volume Refueling – The most unique contribution the KC-10 brings to the joint fight is volume. Launching a single KC-10 provides far more flexibility to any refueling mission because of its longer legs, ability to loiter, and capacity to offload fuel quantities that would require multiple KC-135s or KC-46s. As operations officers and commanders, we lost count of the number of times our KC-10s were supporting a large-scale exercise or senior leader movement where the tanker planners said that the “make or break” refueling was one supported by our units. This was because the offloads required at the critical point could not be accomplished by a KC-135. A primary KC-10 and an additional airborne KC-10 as a backup could easily accomplish a mission which would require at least four KC-135s.

Reach and Deterrence – Perhaps the most concerning aspect of KC-10 retirement is the potential effect on strategic, long-range refueling missions. KC-10s provide huge offload capabilities over long distances, and this is particularly critical in the Pacific where there are relatively few long runways and lots of open ocean to traverse. The Nuclear Posture Review cites the strategic importance of long-range bomber assurance and deterrence missions, “including nonstop, round-trip flights from the continental United States to the Korean peninsula,” for which aerial refueling is “crucial” to success. Those massive fuel offloads are the KC-10’s core asset.

Airframe Life – KC-10s are still relatively young airframes. Compared with commercial DC-10s, the Extender airframe is still at only about 40 percent of its expected lifespan. This is in stark contrast to KC-135s, some of which have been flying since the 1950s, and are scheduled to fly well beyond a normal lifespan.

Stress on the Force – Requiring multiple tankers to complete missions the KC-10 could accomplish by itself will invariably create employ-to-dwell increases and drive continued decreases in aircrew morale. As tanker squadron commanders, we saw firsthand how the demand for air refueling will always outpace our limited supply and how a high operations tempo has a palpable effect on aircrew morale. In a tanker force that is bleeding talent due to the operational stress and endless refueling requirements, more tanker sorties will have a negative impact on Air Force retention.

Parking – This may seem like an odd concern, but limited ramp space could be an operational constraint for large-scale Pacific missions. Any plan requiring KC-10 support could soon require double the number of KC-46s or KC-135s, and there is only so much room to park aircraft at a field. Double the tankers will quickly fill limited ramp space, which is a scarce resource between Hawaii and Japan. Ramp space is also stressing the current tanker bed-down in United States Central Command. Losing a tanker that can carry 356,000 pounds of gas will be a significant planning constraint.

Cargo – The Extender has 27 pallet positions and can carry up to 170,000 pounds of cargo, which is comparable to a C-17. Although it is not normally used in a pure cargo role, the KC-10 can carry its own deployment cargo, freeing up other Transportation Command assets to provide needed lift for the huge wartime logistical requirement.

Simplicity and Economy of Force Smaller tankers require more tails airborne to do the same job. Missions requiring one KC-10 will now require two or even three smaller tankers. Adding tankers to a mission invariably increases complexity of both planning and mission execution. This increases the size and difficulty of both mobility and wartime support missions, thus contradicting two fundamental principles of war. A recent example illustrates this point:

In April 2019, the first-ever tanker formation of a KC-10 and a KC-46 refueled two F-15Es and five F-16s flying from California to Elmendorf Air Force Base, Alaska. The successful mission was rightly lauded as an achievement for the Pegasus; what did not make the press report was the fact that if the KC-46 had not flown, a single KC-10 could have accomplished the entire mission alone, offloading all the gas required for all seven fighters to reach their destination. In fact, the formation was part of an overall plan that utilized six KC-10s to offload 680,000 pounds of gas to 28 airborne aircraft and haul 62,000 pounds of cargo plus 38 passengers. It would require fourteen of the smaller tankers to accomplish the same task. In the near future, what the Air Force has been doing with one refueler will require two. This reality has had many scratching their heads and wondering why the Extender is on the verge of an early retirement.

In light of these operational and tactical considerations, as well as a new strategic focus, the financial decision to retire the world’s largest tanker seems like one suited for a different time and a different context. Furthermore, as the goalposts for divestment continue to be moved down the field due to numerous Pegasus delays and technical problems, it appears there is an implicit reluctance to actually retire this capability. The decision to retire any aircraft should consider not only financial constraints of the United States, but also the strategic and nuclear deterrence requirements that it faces for the future. We believe retiring the big tanker means our military will have insufficient logistical support for key air refueling missions.

Does Everybody Agree … Can We Talk About This?

As leaders in the KC-10 community, we have heard countless discussions about KC-10 divestment. Typically, when the conversation shifts from how the Air Force is going to execute the retirement to why it is doing it, the discussion hits a brick wall. Since the decision has been made, why question it? A fiscally constrained Air Force decided the KC-10 was too expensive, and given the small size of the fleet there is truth to that argument.  But because of the strategic importance of the heavy tanker’s reach and volume, it is worth putting the issue before Congress to settle.

Another argument we hear is that it’s all about “booms in the air.” Many say that the large-volume offloads are a non-factor because volume can be achieved by launching additional tankers. This argument may be true mathematically, but it overlooks a myriad of practical implications that tanker planners and aircrew know all too well. First, there is no planning cell or tanker mission commander who would trade the excess gas in one Extender for additional tankers. Second, more tankers equal more crews and maintainers required to complete the same mission. Third, saying that “the math works out” reinforces a common tendency to disregard logistical details of a plan and then sprinkle them on at the end. Planners refer to this as adding “tanker dust” to the plan. In warfare, booms in the air are important, but so is total offload capability.

Some argue that retaining the KC-10 creates an immediate pilot shortage for Air Mobility Command because all the KC-10 aircrews are projected to retrain into KC-135s and KC-46s aircrews. However, so long as the total tanker inventory remains the same, the shortage won’t worsen because all the tankers have the same number of pilots. In the long run, pilot shortages should be addressed by the growing training pipeline, regardless of airframe. It’s far more difficult to procure new aircraft than it is to train up new aircrew.

Finally, we have heard colleagues suggest that there is no place to put the KC-10s if the Air Force decides to keep them flying. While relocating the KC-10s would disrupt the existing construct, this isn’t without opportunity. One idea is to move the fleet to Global Strike Command where its reach and reserves could be leveraged in support of America’s most strategic platforms. The command relationship for those forces could resemble one recently implemented between Transportation Command and United States Central Command. Then again, perhaps moving the KC-10s completely into the reserve component is the best option, preserving the capability for use when it is needed most. There are multiple options to retain these capabilities.

It’s Not Too Late to Change Course

Do the strategic advantages of keeping the large tanker in the inventory outweigh the costs? In today’s geopolitical environment, we believe they do. In the short term, the United States needs a three-Tanker Air Force, as was its original plan. Unfortunately, fiscal policy trumped strategic requirements at the moment the decision was made. The prospect of a three-tanker Air Force deserves serious consideration, and is an urgent question given the KC-10 divestment timeline. If money remains an issue, senior leaders should make the case to Congress that the Extender is strategically necessary and should be funded until a sufficient large-offload replacement tanker is procured. Discussion and planning on the future basing of the KC-10 should begin immediately. The final decision may be that not all 59 KC-10s are required to meet our strategic needs, but that decision should be made based on requirements, not dollars.

The writing is on the wall — and the question at hand today is not whether we can afford to keep the big tanker, but whether we can afford to lose it.



Lt Col Stewart Welch is an Olmsted Scholar who recently completed two years as 9th Air Refueling Squadron commander at Travis Air Force Base, where he led multiple large-force air-refueling exercises. Col David LeRoy (ret.) served as a deployed KC-10 Squadron Commander at Al Dhafra Air Base, and recently retired as the Vice Wing Commander of the 305th Air Mobility Wing at Joint Base McGuire-Dix-Lakehurst. Both Dave and Stew are instructor pilots with hundreds of hours of combat experience and a combined total of over 6,000 flight hours in the KC-10. The opinions in this article are their own, and do not represent those of the Air Force or the Department of Defense.

Image: Photo by David LeRoy

CORRECTION: A previous version of this article did not mention the small number of KC-135s capable of onloading fuel.