A KC-135 fuels an MC-130J over the Pacific Ocean in November 2019. U.S. Transportation Command is looking to delay the scheduled retirement of some KC-135s until more KC-46s come online. Photo: Senior Airmen Rhett Isbell
Photo Caption & Credits

The Tanker Gap

April 1, 2020

USAF’s budget seeks to swap capacity now for capability in the future, but TRANSCOM is leery. 

The Air Force’s 2021 budget request accepts a near-term shortage in today’s refueler fleet to pay for future capacity. The budget proposal calls for cutting 16 Active-duty KC-10s and 13 KC-135s from the Active and Reserve fleets. 

Meanwhile, the Air Force will continue to buy new KC-46s to keep that production line running, maintaining the current 15-planes-per-year rate even though the new tankers are still years away from being fully operationally capable.  Indeed, Chief of Staff Gen. David L. Goldfein told a Senate committee in March that he would not use the new tankers in war unless absolutely necessary. 

The stress point is the day-to-day demand.Gen. Maryanne Miller, Air Mobility Command boss

“If we go to a high-end contingency, we will put every KC-46 we have into the fight,” Goldfein said, referring to a conflict with a country like Russia or China. “We won’t use it for day-to-day operations, but it will be made available for a contingency.”

For Goldfein, the aim of the 2021 budget—his last as chief—is to build a force capable of fighting and winning in 2030 against both peer threats and violent extremists. 

His “Air Force We Need” plan defines what the Air Force should include to meet the requirements of the National Security Strategy. It calls for a total of 386 operational squadrons, including 40 tanker squadrons. Because the typical tanker squadron includes 12 aircraft, that works out to a requirement for roughly 480 tankers; the Air Force specifies 479. By contrast, today’s force includes 26 tanker squadrons made up of 394 KC-135s and 59 KC-10s, or 453 tankers as of Oct. 1, 2019. That suggests the Air Force has only 65 percent of the squadrons it needs, and only 85 percent of the air refuelers required. (The 33 KC-46s that have been delivered do not count toward that total). If the Air Force gives up 29 refuelers as planned, those percentages get worse.

A second study, by MITRE, predicts the Air Force will need more KC-46s than the 179 aircraft now on order. And the Center for Strategic and Budgetary Assessments, in yet another study, argues the service should delay retiring KC-10s until the KC-46s are ready for operations. CSBA also calls on the service to develop a second tanker platform; for its part, the Air Force is only in the nascent stages of defining the requirements for what has been called KC-X. 

The demand signal for tankers is certainly high and steady. In 2019, USAF tankers delivered almost 950 million pounds of fuel, with an average of 47 tanker sorties daily, according to U.S. Transportation Command. Tankers refueled aircraft every five minutes in Iraq and Afghanistan in 2018, according to the command. Meanwhile, Air Mobility Command says it is flying 15 percent more hours now than it did four years ago—with a smaller fleet and with fewer Airmen. 

Even so, the Air Force and Defense Department leaders in the Pentagon are asking combatant commanders to make do with less capacity in the short term to pay for  future capability tomorrow. 

 “We in the Air Force are looking to the future fight,” said Air Mobility Command boss Gen. Maryanne Miller. “And we have to look at our legacy capacity that we have right now. The idea was, can we give up legacy capacity, still meet the demand today, and still prepare for the future? The stress point is the day-to-day demand.”    

The Air Force’s budget proposal worsens a shortfall that worries combatant commanders and major commands alike, and it will be hard to convince skeptical lawmakers who have repeatedly blocked similar requests in the recent past. 

Goldfein acknowledges the risk, but says the Air Force simply can’t afford everything it needs, particularly the advanced connectivity envisioned for the Advanced Battle Management System that will enable a future Joint All-Domain Command and Control capability. 

“You’ve got to find ways to pay for this,” he said in February, laying the groundwork for his budget arguments. “You have platforms that are not going to play in that 2030 fight. Is there near-term risk, which is real risk, that we need to take as a department to buy our future?” 

Paying for a largely classified digital capability while giving up tangible hardware makes the argument that much harder, he admitted.  “It’s not an easy narrative in a town that’s focused on platforms.”

 Maj. Gen. John Pletcher, USAF’s deputy assistant secretary for budget, argued these cuts are “acceptable risk,” given that they total 488 tankers, above the official requirement of 479 refueling aircraft. In reality, however, roughly three dozen of those aircraft are KC-46s that will remain in operational testing for three or four more years. The new tankers rely on a remote vision system for the boom operator that has been found faulty in certain light conditions. The boom is also incapable of refueling A-10 aircraft, which fly slower and have difficulty maintaining the connection to the boom’s actuator. The Air Force didn’t state its requirements accurately, USAF officials have said, so the Air Force is paying to develop a new actuator. Officials anticipate it will take years to fix these two problems.

Meanwhile, U.S. Transportation Command reports refueling capacity is falling short of operational demand. In a 2018 briefing to industry, the command cited a capacity shortfall of 20,000 to 30,000 refueling hours. Not surprisingly, tankers are high on the command’s unfunded priority list. But tankers were not included on the Air Force’s unfunded priority list, indicating a further gap between tanker consumers in the combatant commands and tanker providers in the Air Force. 

U.S. Army Gen. Stephen Lyons, TRANSCOM commander, told Congress in February the loss of 29 tankers would worsen the tanker capacity shortfall. 

“This creates a capacity gap with significant impacts to combatant command daily competition and wartime missions, and negatively impacts senior leader decision space for mobilization when confronted with a crisis,” Lyons wrote in the unfunded requirements documents sent to Congress. 

The initial fiscal 2021 cuts, and expected retirements of KC-135s and KC-10s in 2022 and beyond, create a “capacity bathtub” until KC-46s come online and are operational. For now, TRANSCOM is asking Congress to reverse the proposed budget cut and “buy back” 23 of the 29 aircraft targeted for retirement, then conduct a “year-by-year review” of the KC-46 before determining any further cuts. Doing so would cost about $110 million, according to the command.

Lyons said TRANSCOM must continually “position/reposition tankers to meet the highest priority NDS requirements while taking risk in lower priority missions. … Limited fleet capacity, an aging fleet with degraded readiness, and non-mobilized operational utilization challenges pose significant risks to meeting future demands.”

Similar concerns were raised last year. 

“We are working closely with the U.S. Air Force to retain sufficient [aerial refueling] capacity and potentially delay the retirement of KC-135 aircraft in order to maintain [a] sufficient number of aircraft to meet operational requirements,” Lyons said a year ago. “We strongly advocate for continued congressional support to enhance tanker readiness and balance new aircraft fielding with aging aircraft divestiture in order to retain the necessary number of accessible AR assets over the next decade to ensure TRANSCOM can meet [National Defense Strategy] demands.” 

Miller expanded on this push last September, saying AMC was working with the Air Force to slow down KC-135 retirements “because I have to keep booms in the air.” Goldfein backed her up at the time, insisting, “We can’t retire [old tankers] until we have an airplane that’s combat-capable.” Pacific Air Forces boss Gen. Charles Q. Brown Jr. (nominated to be the next Chief of Staff) has also emphasized the need for tanking capacity in the 105 million square miles of airspace in which his forces operate, saying more refueling means more flexibility. 

This divide between Air Force and various commands’ planning comes down to different, competing priorities. “For TRANSCOM, they work the day-to-day mission,” Goldfein said, adding that the Air Force is “looking at balancing risk against a stacked portfolio.” 

Mitigating the Risk 

The service is taking steps to try to mitigate these risks, including hiring contractors to fill in some of the gaps. 

Air Mobility Command and TRANSCOM have held multiple industry days to discuss commercial refueling support, meeting with 14 companies in December to provide “boom-type air-to-air refueling” during training, test, and evaluation, and domestic fighter refueling missions. This would free gray-tail refuelers for combat operations and high-level training. 

Senior Airman Derek Chau prepares to drain fuel from the engine of a KC-135 during a routine inspection at Kadena Air Base in Japan. Air Mobility Command is seeking to slow down KC-135 retirements. Photo by Tech. Sgt. Matthew Fredericks

In June 2019, TRANSCOM detailed a requirement for contractor-owned and -operated aircraft for both boom and hose-and-drogue refueling, to meet an operational demand of about 7.6 sorties per day. Contractor discussions are ongoing, but no contract has been awarded, according to AMC.

Miller said the command finalized a feasibility study on the possible award in March, which in turn would inform a formal request for proposals. The initial goal would be a contract within a year of the RFP to cover about 6,000 flight hours. There’s a hiccup in this planning, however. The Federal Aviation Administration needs to be involved and sign off on the safety regulations for private aircraft refueling military planes. “The FAA is really averse to having two airplanes very close together,” Miller said.

AMC is also trying to figure out how to wring more efficiency from the tankers it has. By leveraging existing data and machine learning, the command aims to get smarter about how tankers are tasked, getting more usable refueling hours downrange from each flight. AMC is using historical data to predict when the demand for booms is greatest, and how to support those peaks and valleys. From July 2018 to early March 2019, that effort meant reducing by nine the number of KC-135s in theater and saving 17 KC-135 crews. Likewise, the command reduced by two the number of KC-10s in theater, saving six KC-10 crews. Potentially, this could reduce the required number of aircraft, but for now it has other impacts.

“This allows our most stressed force to improve quality of life and squadron vitality, while finding additional time to maintain full-spectrum readiness,” AMC said. 

While the service has not identified the specific airframes it would like to retire, a service spokeswoman said the selected aircraft would be the “least ready” in the fleet. The entire tanker force is old: KC-135s average about 57 years old and the KC-10s average 34. 

A KC-135 extends its boom toward a KC-46 during a rendezvous in August. Delays in operational capabilities for the KC-46 mean USAF is scrambling to keep booms in the air. Photo: Staff Sgt. Mary McKnight

Those aircraft that remain will benefit from continued investment. The Air Force budget request includes $88.25 million for Block 35 upgrades to the KC-135, but only $117,000 for KC-10 modifications.

The Air Force needs to look to the future and what capabilities will be relevant. 

“We’ve got to do the trade here,” Goldfein said, lamenting a lack of funds to pay for all his needs. “The risk is real. If we had money, we wouldn’t be asking the combatant commanders to take short-term risk.”