How the sixth-generation fighter jet will upend air warfare

The next generation of fighter aircraft could bring greater speed, range and ability to penetrate deep into enemy airspace — and it might even feature a revolutionary new type of engine , experts and retired U.S. Air Force officer say.

The aviation world has seen five generations of fighters, ranging from the subsonic F-86 Sabre after World War II to the current, stealthy F-35 Joint Strike Fighter. Now, militaries around the world are working on jets they believe will represent technological leaps significant enough to qualify as sixth-generation aircraft .

And while the precise definition of a sixth-generation aircraft isn’t set in stone yet, experts agree on some common attributes , retired Air Force Lt. Gen. Clint Hinote told Defense News.

The Air Force’s effort to build a sixth-gen fighter family of systems is known as Next Generation Air Dominance, or NGAD, and experts say the platform will be asked to do a lot of things.

“You want it to be fast, you want it to fly high,” said Hinote, who was the Air Force’s former deputy chief of staff for strategy, integration and requirements. “You want it to fly a long way. You want it to be as stealthy as possible — not only in radar frequency … [but also] in the infrared spectrum as well.”

Hinote and Heather Penney, a retired F-16 pilot and senior resident fellow at the Mitchell Institute for Aerospace Studies, said speed, stealth and range will be among the most crucial elements of a sixth-generation fighter — particularly if it is needed to cross long distances in the Pacific and enter Chinese-controlled airspace.

“Range and the ability to penetrate will be absolutely critical for sixth-generation aircraft, especially given that we’re looking at the Pacific theater and China as our primary pacing threat,” Penney said.

Fifth-generation aircraft such as the F-22 and F-35 were conceived at a time when the United States military still had a Europe and NATO-focused mindset, Hinote said.

“The [F-35] requirements were basically developed right after the Cold War,” Hinote said. “It’s a short-range fighter. That makes total sense in NATO, where you’ve got hundreds of runways everywhere to operate off of. It makes no sense in the Pacific, where the situation is much different [and] you only have a few runways to operate off of.”

It needs to be able to communicate without giving its position away, Hinote said, and it must be able to carry larger payloads than fifth-generation aircraft carry today.

“That allows you to get to a position in the battlespace and the airspace where you can enforce your will through the use of force, if necessary, the concept of air superiority,” Hinote said.

And the ability to maintain a plane without damaging its stealth coating will be crucial, Penney said.

Early versions of stealth technology on aircraft such as the F-117A Nighthawk and B-2 Spirit bomber were delicate and difficult to maintain, she said.

Stealth has made considerable leaps forward over the years to be more practical and reliable, Penney said, and a sixth-gen fighter’s stealth capabilities also need to take another step forward to be maintainable and provide better performance.

Hinote and Penney said the next generation of aircraft must both take in large amounts of detailed data and fuse it in a way that sorts out the battlespace.

A sixth-gen aircraft “should be able to not only have those advanced sensors, not just forward looking, but side and aft, looking across [multiple] phenomena” such as radar, infrared and other frequencies, Penney said.

And the Air Force wants NGAD to team up with AI-operated drone wingmen known as collaborative combat aircraft, or CCA, as part of the “family of systems” concept. CCAs could carry out strike missions, jam enemy radars, conduct recon, or even serve as decoys.

The Air Force has so far planned for NGAD to have a new type of propulsion system known as an adaptive engine , which can shift to different, more efficient configurations depending on the flying situation. Pratt & Whitney and General Electric Aerospace are each developing their own adaptive engines as part of the Next-Generation Adaptive Propulsion program.

An adaptive engine, however, would be very expensive, Hinote said. And with serious budget crunches prompting the Air Force to reconsider its plans and designs for NGAD, the service is considering whether to scale down its engine to bring NGAD’s price down.

Air Force Secretary Frank Kendall said in a June interview with Defense News that making NGAD’s engine smaller and less complex is an option being considered.

But better dogfighting ability would likely not be on the wish list for sixth-generation fighters, Hinote said. He does not expect those aircraft to have advancements in slow-speed maneuverability or an emphasis on cannons that would allow fighters to go toe-to-toe in relatively close quarters.

“The F-22 can get a high [angle of attack] in ways we’ve never seen,” Hinote said. “The Sukhoi Su-57, same thing. I don’t think it’s relevant for enforcing air superiority in the Pacific.”

The Defense Department does not keep a hard-and-fast taxonomy of aircraft generations. But in 2017, a spokesman at Joint Base Langley-Eustis in Virginia took a crack at it.

In his column, Jeffrey Hood of the 633rd Air Base Wing’s public affairs office said the first generation of fighter jets that emerged following World War II took advantage of novel jet technology and swept wings, as opposed to the perpendicular wings that were previously standard. But those fighters, such as the F-86 Sabre, were limited to sub-sonic speeds and machine guns.

All that changed after Chuck Yeager broke the sound barrier in 1947. This opened the door to a second generation of jets, such as the F-104 Starfighter, that could break Mach 1 and even Mach 2, and carry on-board radar and air-to-air missiles, Hood wrote.

The third generation — which included the Vietnam-era F-4 Phantom — incorporated advanced radars and better guided missiles that could engage enemies beyond visual range. After that came the F-14 Tomcat, F-15 Eagle, F-16 Fighting Falcon, and F-18 Hornet — fourth-generation fighters that can maneuver at high G-forces, use digital data links to share information, track multiple targets, and strike surface targets using lasers or GPS guidance.

In a 2016 study published by the Mitchell Institute for Aerospace Studies, now-retired Gen. Jeff Harrigian said fifth-generation fighters such as the F-22 and F-35 include stealth, improved self-defense, sensing, and jamming abilities, integrated avionics, and more.

And depending on one’s perspective, the first sixth-generation aircraft could already be flying.

Northrop Grumman has touted its B-21 Raider bomber as the first sixth-gen aircraft. In an interview with Defense News before the B-21′s 2022 rollout, a Northrop official said the bomber’s cutting edge stealth, use of open systems architecture, and use of advanced networking and data sharing technologies to connect sensors to shooters across multiple domains make it “the first of the sixth-gen systems.”

Those abilities are probably enough for the B-21 to qualify as a sixth-generation aircraft, Penney said, though she said its high levels of classification make it hard for outside observers to gauge whether it lives up to the hype.

Hinote looks at Northrop’s claims with a bit more skepticism and thinks it’s more of a marketing angle, but notes these generational definitions are largely matters of opinion.

“If they want to call it sixth-generation, sure,” Hinote said. “I don’t necessarily believe that the stealth characteristics and the open architecture of the B-21 automatically makes it a generational change in what we’ve got. It’s an incremental step, it’s a good step, I’m glad that we’re doing it, but it’s probably not so big that it’s truly generational.”