The world's top military powers each have fifth-gen jets, but Russia, China, and the US are all facing problems with their fighters

• Russia, China, and the US all have fifth-generation fighter jet programs.
• The Russian Su-57, Chinese J-20, and American F-35 are all facing various challenges.
• Business Insider spoke with several experts about what's been holding these programs back. 

The world's top military powers have been working to develop formidable fifth-generation fighter jet fleets for decades, and that's still a work in progress.

The US built the first fifth-generation fighter, the stealth F-22 Raptor, and it followed that project with the F-35 Lightning II Joint Strike Fighter. Russia and China have the Su-57 and J-20, respectively.

The American F-22 is no longer in production, and the three newest jets, all of which are regarded as fifth-gen jets even if some of them don't quite check all the boxes, are each facing challenges.

To qualify as a fifth-generation fighter, an aircraft needs to have certain features like stealth capabilities to avoid detection and the ability to cruise at supersonic speeds without engaging its afterburners, among other things.

Aviation experts outlined several issues with the Russian, Chinese, and American fifth-generation programs — including problems with stealth technology, engine development, and maintenance — in recent interviews with Business Insider.

Russia's Su-57

The Sukhoi Su-57 is Russia's first attempt at a fifth-generation fighter aircraft, but analysts have questioned if it actually qualifies for this distinction given its shortcomings in several key categories.

Known to NATO as the 'Felon,' the Su-57 was delivered to the Russian military in 2020. There are said to be only 10 aircraft in Moscow's arsenal, but state media suggests this figure will increase to 22 by the end of 2024 and jump again to 76 by 2028. It's unclear if those plans will hold though.

The Su-57 first saw combat experience above Syria in 2018. Last year, Russian officials claimed that the aircraft had seen combat experience in Ukraine, which is backed up by intelligence published by Britain's defense ministry. But while the jets may have engaged in some standoff attacks, there isn't really any evidence of widespread Su-57 employment in the ongoing war.

One explanation for the lack of participation in the kind of war that fifth-generation jets were built for could be that the Russian jet lacks the low-observable characteristics that would allow it to operate as a proper fifth-generation fighter. Issues with the aircraft include Moscow's apparent struggle to outfit it with stealth-capable engines and tightly placed body panels that would adequately reduce its radar signature.

Ultimately, Russia's reluctance to use its Su-57s in Ukraine "suggests that they do not have confidence in the claimed stealth properties of the jet," Justin Bronk, an airpower expert at the Royal United Services Institute (RUSI) think tank, previously told Business Insider.

Additionally, he noted, the aircraft can only carry an older variant of the R-77 air-to-air missile. This has "folding grid fins that prevent it from being carried internally on the aircraft and hence compromises its stealth signature," he said.

China's J-20

China, as the so-called "pacing challenge" for the US military, also has a fifth-generation fighter program. Six years after making its first flight, China's Chengdu J-20 entered service in 2017.

There, it joined Beijing's inventory of 1,900 fighter jets and has since been "operationally fielded," according to a 2023 Pentagon report on the country's military power. It is estimated that China has built more than 200 J-20s and is preparing several upgrades for the fighter, among them being the installation of domestically produced WS-15 engines.

The capable WS-15 is the engine that the J-20 was originally supposed to have because it would allow the fighter to fly at supersonic speeds without engaging afterburners and lend the aircraft some additional stealth capabilities. But the Chinese defense industry has long struggled to manufacture the advanced engine, so the military has used older Chinese engines and Russian ones instead.

"The J-20 engines have been a big headache, but I think they're indicative of larger challenges within the Chinese defense industry," said Mike Dahm, a former US Navy intelligence officer. "For all of China's technological progress, they still lag behind the West in high-end manufacturing techniques, whether it is engines, low-observable materials, or metallurgy."

"Precision manufacturing," he said, "has an outsized impact on stealth and fifth-generation aircraft capabilities."

Despite earlier setbacks, the J-20 appeared to fly with a pair of WS-15 engines this past summer in a milestone moment. But Dahm, a senior resident fellow at the Mitchell Institute for Aerospace Studies, cautioned that even if China has managed to overcome its manufacturing challenges, the reliability of the WS-15 engines is still questionable and could cause problems — especially if it's not built to the same tolerances as Western aircraft.

"Over the course of the engine's lifetime, they will have to perform maintenance on their engines more often and will probably have to replace the engines more often," he said. "Those maintenance challenges will ultimately impact the readiness of the aircraft and the availability of the aircraft."

Michael Bohnert, a licensed engineer at the RAND Corporation think tank who has supported analysis work for the US Air Force, said maintenance of stealth materials — like applying coating on an aircraft — is an expensive and "painful" process that requires a lot of investment, both from a labor and infrastructure perspective.

"Having stealth aircraft is more than just the plane," Bohnert said. "It's the missiles, the tactics, it's the logistics, it's the maintenance infrastructure — there's a lot that goes into it. It's a long train to get there, and you can choose not to follow it."

Like the Russians, China is still relatively new to the fifth-generation fighter game. But even the US, which has had a fifth-gen jet since 2005, is having challenges with its new Joint Strike Fighter.

America's F-35

Developed by defense manufacturer Lockheed Martin, the F-35 is the second fifth-generation fighter in America's arsenal after the F-22 Raptor and comes in three variants.

The US Marine Corps F-35B is capable of short takeoffs and vertical landings and was first achieved initial operational capability in 2015. The F-35A is used by the US Air Force and achieved IOC in 2016 while the F-35C is employed by the US Navy and was operational by 2019.

The aircraft, which was built for ground attacks, air-to-air combat, and networked airpower, has patrolled in Europe and the Pacific and seen some combat experience in the Middle East.

The fifth-gen plane is operated by both the US military and a number of US allies. Israel was actually the first nation to fly the jet in combat.

The US military has around 450 F-35s and the Pentagon plans to procure approximately 2,500 more over the next several decades; the estimated life cycle cost is more than $1.7 trillion — much of which will go to operating and repairing the aircraft.

This very expensive program has been plagued by maintenance and sustainability issues that have often impacted the fighter jet's readiness, and that continues to be the case, according to a September report published by the Government Accountability Office, or GAO. Earlier this year, for example, the aircraft was capable of flying missions barely over half the time.

The report identified several specific issues at military installations, including a lack of support equipment, spare parts, adequate training, and technical data — all of which can contribute to maintenance delays. The report also found that the F-35 program was behind schedule in establishing facilities to conduct repairs and that the US government has relied heavily on contractors, which reduces its own ability to make decisions.

An overarching problem is that for many years, the F-35 program was focused on production, said Diana Maurer, the director of defense capabilities and management at the GAO. The priorities were largely about research, development, and acquisition, while sustainment and its costs were downgraded to a later focus. These problems are now in play.

"The F 35, when it was becoming operationally available to the services, did not have the depot repair facilities up and running to fix the aircraft when it was needed to be repaired. Even now, the program is still years behind in completing depot standup," Maurer said. This means that when major parts of the aircraft need to be repaired or replaced, they often times need to go all the way back to the original equipment manufacturers.

"That creates a lot of delays," she said. And because it takes longer to repair those parts, the backlog grows, and the aircraft becomes "less able to fly across the entire fleet."

The GAO has made several recommendations to the Pentagon in a bid to alleviate some of the challenges, including reassessing the breakdown between government and contractor responsibility. If there is any change to this balance of oversight, the GAO suggested in its September report that the Pentagon figure out what sort of technical data or intellectual property it might need.

Adding to the F-35 program's woes, a December GAO report determined that there are issues with the fighter's cooling system. In particular, it's overtasked, operating beyond what it's designed to do, which could increase wear on the engine, reduce its life, and add billions in maintenance costs.

"It's really important for the US to get a grip on the F 35 program. When it is flying, we've heard from pilots that they're very happy with the capabilities of that weapon system," Maurer said, adding that "it's not just the future of combat aviation for three of our military services — it's the present."