The Air Force wants to modernize air refueling, but it’s been a bumpy ride

An inside look at how these old planes work—and how the tech underpinning the fleet is slowly evolving.
an F-22 fighter jet
An F-22 fighter jet flies near the refueling boom of a KC-10 tanker. Rob Verger / GoPro still

The first F-22 approaches from behind our KC-10 tanker aircraft, subtly camouflaged and eerily quiet thanks to the tanker’s ambient noise. We’re cruising thousands of feet above the Atlantic, going hundreds of miles per hour, and the F-22—a stealth fighter jet known as the Raptor—slowly closes the gap, sliding up toward a refueling boom that hangs from the rear and bottom of our plane. 

The KC-10 tanker is a flying gas station, a cargo aircraft capable of offloading thousands of pounds of fuel into receptacles atop planes like the Raptor. Holed up in a cozy compartment in the tanker’s rear, a human—in this case Sebastian Dewsnap, a member of the Royal Australian Air Force on exchange in the US—watches through a rear-facing window to operate the telescoping delivery system.

This is how the Air Force has handled refueling for decades: with a person like Dewsnap looking out through glass at a thirsty plane. But KC-10s like the one we’re flying for this training mission in November of 2021—and the KC-135s the Pentagon deployed to the EU just this week—are at a point of transition: The KC-10 is set to be retired over the next two years, with the KC-135 flying off into the sunset sometime long thereafter. The intended replacement, called the KC-46, relies on a higher-tech tactic: A remote-vision solution will replace Dewsnap’s rear window. Someday, tankers like this could do away with boom operators entirely in favor of partially, or fully, robotic systems.

Dewsnap, in the foreground, working in the boom compartment of the tanker. Rob Verger

An aging fleet filled with aging tech 

After that first Raptor arrives, over the next seven minutes or so, and through multiple attempts, the pilot tries to maneuver his stealth aircraft in the right place below the tanker. Meanwhile, Dewsnap plays the role of attendant at the flying gas station. Using his right hand on a joystick-like controller, he can manipulate the boom’s position—side to side, up and down—and with his left, he can telescope a portion of it outward to insert into the fighter. Eventually, having connected enough to take on some 4,900 pounds of fuel, the fighter falls back and banks away. 

“Here comes the other one,” Dewsnap says, as another Raptor floats in and approaches the boom. 

You may not have considered the fact that air refueling exists, because it never happens on commercial flights: Airliners lack the necessary hardware to receive fuel in the air, and there would be no reason for them to take on the extra risk of fueling in the sky when they can just gas up on the ground for their routine, predictable journeys. But for the military, it’s a long-established way to give a fighter jet, bomber, or other aircraft the petroleum product it needs to keep going for very long distances without landing. “It’s a fundamental enabling capability for all militaries that operate an air force,” says Todd Harrison, the director of the aerospace security project at the Center for Strategic and International Studies. Indeed, four US Air Force KC-135s have just arrived in Germany following Russia’s Ukraine invasion, though the Pentagon’s statement doesn’t specify what aircraft the tankers may support.

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It’s a transitional time for these fuel-schleppers. The KC-10 that Popular Science caught a ride on has been in the Air Force’s inventory for some 40 years. The KC-135, which makes up the majority of the Air Force’s fleet of more than 400 tankers, has an average age of about 60, according to a recent report from the Government Accountability Office. “You just can’t keep [the KC-135] planes flying that much longer—they have reliability problems, they have maintenance challenges, they’re expensive to operate,” Harrison says. 

Between the KC-10s and the KC-135s, “we have a small fleet that’s old, and we have a large fleet that’s extremely old,” Harrison says. In the KC-135s—which despite their advanced age will stay in service for many more years for logistical reasons (although some will be retired as new aircraft come online)—boom operators lay down at the rear of the aircraft and look out through windows at the scene below them. But while they’re slightly newer, the Air Force is retiring the KC-10s first: There are far fewer of them (just 47) than the KC-135s, so it’s easier for the military to phase them out, in part because smaller fleets are more expensive to maintain on a per-plane basis. The KC-10s will fly only through 2024.

“The KC-10 has been definitely a workhorse for the US Air Force,” Dewsnap said before takeoff that day, standing on the tarmac, arms crossed. “It’s sad to see it go to pasture.” 

The ground crew fixed a fuel leak in engine number three on the KC-10 before the flight. Rob Verger

The quirks of the decades-old KC-10 were on full display before it lifted off the ground from McGuire Air Force Base in New Jersey to fly south to meet the Raptors. The first problem was a fuel leak in one of the engines; the ground crew fixed it. The second problem occurred after the aircraft had already started taxiing. Each of its three engines has a generator, and those generators are supposed to operate in sync with one another. But they weren’t parallel with each other. After troubleshooting it, and nearly not being able to take off, the cockpit crew finally fixed the glitch by resetting the generators. 

Tech. Sgt. Justin Lassiter, the flight engineer, had to navigate an issue with the generators. Rob Verger

The new bird is the Pegasus 

That isn’t to say that the KC-10’s looming replacement is perfect. Anything but. The KC-46 has been entering the fleet like the glitchy robotic new kid on the block. The Pegasus has been very problematic for the Air Force, mainly because of a major design change: instead of sitting at the back of the aircraft and looking through a window, operators get their information from a remote-vision system by way of a screen. 

That remote vision system, or RVS, has been tough to refine. “The biggest problem that it had was, as it began to be developed and fielded, camera technology was not where we thought it might be,” says Brig. General Ryan Samuelson, who heads the Air Force’s acquisition and operations process for the KC-46. “When we fielded it, we realized under certain sun angles, under certain reflections off of water, clouds, the cameras would start to wash out.”

Boeing concedes that the tech is now dated; the company received the contract over a decade ago. “We had basically 2010 technology that we had to build and produce [the aircraft with],” says Mike Hafer, Boeing’s business development senior manager on the KC-46 program. In 2020, Boeing and the Air Force agreed that the airplane maker would put in a new vision system. Specifically, the RVS includes two regular-vision cameras, plus two infrared ones to employ during nighttime refueling. Boeing promises a better system is coming. “This will be 4K, ultra-high-def cameras and displays, as well as the video processors, with fiber optic cable in between,” Hafer adds. 

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The KC-46 originally arrived with what’s now called RVS 1.0, and the final goal is to start fielding the new system with those 4K cameras, RVS 2.0, in 2023 and 2024. A bridge system that the Air Force calls “enhanced RVS” will use software changes to mitigate the problems before the new hardware arrives. The current setup is reportedly hard to use. As one reporter said after flying in a Pegasus last year: “It’s hard to really describe the challenges boom operators have with the current set up.”

“Big picture on the KC-46 program,” Harrison, of CSIS, reflects, “is Boeing thought that it would require less development work to produce an aircraft to the Air Force’s requirements than it ended up being—not only did it cost more, it also took longer—much longer than anticipated.” 

Even today, the KC-46 has a total of seven major problems and has been the subject of multiple reports from the Government Accountability Office. These “critical deficiencies,” as the GAO describes them in its most recent report on the tanker, “are shortfalls that could cause death, severe injury, or illness, or otherwise cause loss or damage to the aircraft.” Two of those critical problems pertain to issues with the remote vision system. 

“The majority of those will either be certified and/or closed this year, to next year,” Hafer, of Boeing, adds. “RVS is the long pole in that tent, and we’re on path with the Air Force to close that by 2024.”

The GAO outlines the major problems remaining with the KC-46. Courtesy Government Accountability Office

Boeing has lost more than $5.4 billion on the jet, which they boast offers a much more modern tanker for the Air Force—from better mission planning, to more advanced data sharing, to protection against an electromagnetic pulse, to armor that shields the flight deck. “It’s ready to go to war,” says Hafer. The caveat to that statement is that right now, the Air Force isn’t comfortable using the tanker to refuel fighter jets like F-35s or F-22s during actual military scenarios (as opposed to training exercises) for fear that the wonky boom system could scratch those aircraft’s fancy stealth coatings. 

Another KC-10 took part in the training flight. Rob Verger

Could automation do the job?

All of this raises the question: Why shift away from the simplicity of a window in favor of a newfangled remote vision system? Harrison speculates that this is meant to pave the way for completely automated future systems. “First step towards an automated boom is using a camera—using a synthetic system—for control of it,” he says. “That’s what I think it’s really a first step towards, is getting towards automated boom operations, and completely remotely piloted aircraft.” 

Right now, the Navy is trying out an aircraft for just that: a Boeing-made refueling drone called the MQ-25. And a tanker from Airbus has a similar setup to the KC-46, with the boom operator sitting up front. They already have transferred fuel from the tanker to a receiver using their automated system. 

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Samuelson, of the Air Force, says his service branch could see more automation in his lifetime. He reflects that “it is absolutely in the art of the possible” that “automation—whether it be automation in the flight control systems or automation in offload of data or fuel—will be something that the US will have in its inventory.” 

Boeing echoes that assessment more decisively. “As we revamp that entire system, we are installing the architecture that will allow a transition into autonomous air refueling,” Hafer says, “so that you can either have the boom operator assisted by the computer, and/or have the computer fly and do the air refueling in and of itself.”

Automating a tanker completely is something that Harrison, of CSIS, thinks makes sense. “Aerial refueling is very tedious and routine and boring, and so if we can make this uncrewed, we absolutely should.” 

a kc-10
Each KC-10 tanker can also receive fuel. Rob Verger / GoPro still

‘I grew up with this airplane’

That day in November, aboard the KC-10, the air refueling operation proceeded through its intricate dance. Dewsnap spent more than an hour gassing up the F-22 Raptors—which had call signs like Bobcat 2 and Oxen 1—offloading a total of around 75,000 pounds. It took place at some 28,500 feet, cruising at around 500 mph. 

Speeding through the air while other aircraft maneuver close behind you is enough to make one wonder if the operation is dangerous. “Anytime you fly two aircraft close together is risky,” Dewsnap says, before takeoff. “There is potential for stuff to go wrong, and that’s why we train so much.” 

Later, in a break between refueling the Raptors—after Bobcat 2 drifts away, and before another arrives—Dewsnap reflects for a moment. “That was hard work,” he says. There were a lot of communications over the radio to juggle, and one of the receivers “wasn’t staying on the boom.”

We finish giving the fighter jets the fuel they need, then practice with another KC-10 tanker (the vessels are also capable of receiving fuel in flight). We fly up close behind the other large metal bird, visible right there through the cockpit windows. Its colorful boom hangs below. We go through the motions, though no liquid changes hands. 

In the early afternoon, after about four hours in the air, we come in for a landing. The KC-10’s shadow flies across the trees below, visible through a window on the left side of the cockpit. An automated voice calls out our altitude over the ground as we descend. We make contact with the runway. Everything shakes. We are back on the ground in an aircraft that isn’t too long for this world. 

Lt. Col. Paul Murphy, one of the pilots and the aircraft commander that day, reflects on the KC-10 after we land. “I grew up with this airplane,” he says. “I chose this airplane to fly out of pilot training. It’s kind of hard to see it go.”

Watch footage from the flight, below.