Russia’s Sukhoi Su-57 is one of only four operational 5th generation fighters anywhere on the planet, keeping the rare company of China’s Chengdu J-20 and America’s Lockheed Martin F-22 and F-35. Each of these fighters was developed with different specialties in mind, but share a collective focus on a few specific design elements that have come to define their generation of aircraft, including stealth and data fusion capabilities.

There’s little doubt that America’s stealth fighters are the best in the world, with China continuing work on the WS-15 engine they believe will bring the J-20 on par with America’s dogfighting champion, the F-22 Raptor. The F-35 Joint Strike Fighter, on the other hand, isn’t an acrobatic prize fighter like the F-22, nor is it a long-range interceptor like the J-20. It is, however, an incredibly sneaky flying supercomputer that can make other platforms in the area more lethal through its presence. Russia’s Su-57 is widely seen as the least stealthy of the 5th generation entrants, but there’s more to a fighter jet than radar cross-sections.

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Comparing these jets to one another in a head-on way doesn’t really do any of them justice, as none were intended to operate alone in contested airspace full of opposing fighters. Each of these platforms was developed to fill a role within a broader force structure and strategy, and as such, are unlikely to run across one another one-on-one in even the most dramatic of scenarios. Of course, that doesn’t mean we can’t compare these fighters on paper, it just means that which fighter would win in a Top Gun-style dogfight isn’t quite as important as which offers a greater jump in capability for the forces it supports.

All that is to say that, the Su-57 might just be the worst 5th generation fighter on the planet… but that doesn’t make it a bad fighter at all.

PAK FA: The troubled beginnings of the Su-57

The long road to the first Su-57 taking to the skies began in 1979 under the former Soviet Union, with plans to field a next-generation fighter that could enter service in the 1990s. However, the collapse of the Soviet Union in 1991 practically halted progress on the program, leaving America’s F-22 Raptor to claim the title of first stealth fighter unopposed with its first flight in 1997. Real development on the modern fighter program began once again in earnest in 2002, with America’s F-22 set squarely in the program’s sights.

By 2007, Russia’s PAK FA program, which was short for “‘prospective aeronautical complex of front-line air forces” in Russian, was once again steaming toward fielding a real stealth fighter. India, keen to have their own 5th generation aircraft, agreed to team up with the Russians to continue development and begin procuring what would eventually become the Su-57, but the partnership wasn’t to last.

In 2018, the Indian government signaled their departure from the program despite Russia’s promising claims about their first batch of prototype fighters, and while India’s official reasons didn’t suggest problems with the program itself, unofficially, rumors swirled that India had given up the PAK FA program because the fighter it produced simply wasn’t stealthy enough to survive in highly contested airspace, alongside a list of other concerns.

Nonetheless, Russia persevered. A total of 12 prototype Su-57s were constructed for testing and assessment, and just months after India backed out of the program, Russia’s Defence Ministry signed a contract to purchase the first two serial production Su-57s, slated for delivery in 2019 and 2020. Russia had already placed their prototype fighters in “operational service,” deploying them to Syria for little more than headline fodder and a few promotional photos, but these first two production jets were to be something more: They would not only represent Russia’s top-of-the-line fighters, they would be the nation’s first-ever production stealth aircraft.

The first production Su-57 crashed before it could even be delivered

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In December of 2019, just days before the Russian military expected to receive their first serial production Su-57, the program was met with yet another dramatic setback. Sukhoi, the firm tasked with developing the Su-57, was conducting flight testing with the fighter to ensure it met the requirements for delivery when the aircraft crashed just 111 kilometers from the airfield it departed from.

The pilot, a civilian contracted with Sukhoi, ejected and survived, but the aircraft was a total loss. In the days that followed the crash, Russian investigators would cite a failure of the tail’s control surfaces for the incident, limiting the pilot’s ability to control the aircraft. According to Russian media outlets, the aircraft exploded upon impact with the ground.

It was a significant setback for a fighter program that had already spanned nearly five decades in its various iterations and a huge blow to Russia’s fragile reputation as a global military power. Shortly after the crash, Igar Ozar, the CEO of Sukhoi, resigned from his position.

That wasn’t the fighter’s only issue with production

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One crash isn’t the extent of the Su-57’s production woes, however. The Russian government still projects to receive as many as 76 of the stealth fighter this decade, but while they were intended to field an advanced engine system designed specifically for the aircraft’s stealth role, delays in the engine’s development have hindered progress. It’s now expected that each Su-57 delivered to the Russian Air Force for the foreseeable future will come fitted with the Saturn AL-41F1 engine also found in the 4th generation Su-35S.

Not only does operating an older engine limit the performance of the Su-57, it also has a detrimental effect on stealth. Contrary to popular understanding, stealth isn’t a single technology or piece of equipment, but is rather a variety of overlapping technologies, production methodologies, and combat tactics. Defeating detection and weapons lock isn’t just about radar, it’s also about infrared heat signature–and the 4th generation engines designed for non-stealth aircraft employed in the Su-57 aren’t good at masking either.

And it’s not just with stealth and propulsion that the Su-57 continues to lag behind the competition. One of the aircraft’s selling points has also been its sensor suite and advanced avionics — with the Russian government claiming the fighter is capable of full 360-degree sensor coverage much like the flying supercomputer F-35 Joint Strike Fighter. To date, it does not appear that any such system is online in the Su-57, with the Rand Corporation analysis positing that sanctions placed on Russia after its military annexation of Crimean in 2014 have further hindered the system’s development.

What is the Su-57 really capable of?

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It’s always difficult to divine real combat capability when analyzing programs like the Su-57. It’s difficult enough with a program like the F-35, which benefits from a concerted marketing campaign aimed at keeping the taxpayer happy with their investment and presenting the aircraft as a worthwhile purchase for foreign allies. It’s even more complicated in a nation like Russia, where news media is strictly controlled by the government. As a result, what we know for sure about the Su-57 and its capabilities is a shorter list than what we’re pretty confident about through analysis of open-source information, news reports, images, and video of the aircraft.

That is to say that any concrete breakdown of the Su-57’s capabilities should be taken with a grain of salt. Those who claim to know for sure what the aircraft can do are relaying numbers and data provided to the public by Sukhoi by way of the Russian government–who, like the United States, is counting on foreign sales of the fighter to offset the high cost of the plane’s development and production. In other words, Russia has at least two motives to present the Su-57 as more capable than it is: to present an image of military might in the face of Western opposition, and to entice potential buyers who want a stealth fighter but aren’t allowed (or can’t afford) to pursue the F-35.

But despite the marketing smokescreen, there are a number of things we can glean about the Su-57 and its capabilities.

It’s ranked last for stealth

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While exact figures regarding the radar cross-section of the Su-57 aren’t available, the aircraft’s design is indeed stealthy… but stealth isn’t something you have or don’t have, it’s really more like a spectrum. Aircraft can be stealthier or less stealthy than others based on a variety of variables ranging from production tolerances in the fuselage construction to the direction from which they’re being observed. The Su-57’s stealth is hampered by Russia’s struggle to bond body panels of the aircraft as tightly as necessary to inhibit a radar return and by its modified 4th generation engines.

The Su-57 ranks last in stealth among its 5th generation counterparts, but that doesn’t mean its stealth capabilities should be utterly dismissed. Again, in combat, it’s not about whose fighter has the smallest radar cross section or infrared signature, it’s about leveraging these platforms for maximum effect, and the Su-57 wasn’t designed to serve as stealthy scrapper like the F-22.