With a NATO war and Ukraine's knack for shooting down planes in mind, Russia is holding back its airpower and most advanced jets

• Russia is holding much of its airpower and more-advanced jets in reserve, defense experts say.
• One concern for the Russians is Ukraine's air defenses, which have shot down a number of Russian aircraft.
• Another consideration is that these assets could be needed in a larger potential war with NATO.

Russia has kept much of its airpower and some of its most advanced aircraft out of the war in Ukraine. Defense experts say doing so signals Russian worries about Ukraine's air-defense game but also considerations beyond this fight to one with NATO.

John Baum, an airpower expert at the Mitchell Institute who's a retired US Air Force lieutenant colonel, told Business Insider that the Russians "could bring more-advanced aircraft into the fight" but that "they simply haven't done that yet."

Some Kremlin claims aside, there's no evidence Russia has used its Su-57s over Ukraine itself, despite the aircraft, at least on paper, being Russia's most advanced plane and supposedly built for a war in which the airspace is heavily contested.

The jet is Russia's first attempt at a fifth-generation fighter, touted by Russian media as a match for American fifth-generation stealth fighters such as the F-22 and F-35. But given limitations in the design, such as a lack of all-aspect stealth, analysts question whether the plane's actual capabilities fit that description. The aircraft also suffers from some lingering technical issues.

In January, the UK Ministry of Defence said the Su-57 had been limited to launching missiles from Russian territory, mirroring how Russia has used many of its other aircraft in this war.

Unlike the ground troops it throws into the "meat grinder," Russia tends to use its air assets in ways that minimize risk by keeping them back from Ukraine's defenses.

"Russia is husbanding a lot of its air assets. So, a lot of the Russian Air Force, you are not even seeing over Ukraine," Andrew Curtis, an independent defense researcher who spent 35 years as a UK Royal Air Force officer, said. He added that Russia had been using Su-57s in ways that posed "no risk."

"The reason for that is simply that it is keen to make sure that it retains a credible modern air force for any future operations that it might want to undertake," Curtis said.

"And that in itself is quite significant," he added, "because it shows that at least somebody in the Kremlin is thinking beyond just Ukraine."

Russia is holding back its air forces with NATO in mind

Michael Clarke, a Russia and Ukraine expert who's also a UK national security advisor, said Russia was making some sacrifices in Ukraine for a possible future conflict. "If the Russians were throwing everything they had against Ukraine, they would probably be in a stronger, better position than they are now," he said.

He added that Russia's air force was holding back jets "because if it devoted all to Ukraine, it feels it will have nothing left if it comes to some sort of conflict with NATO."

The top US commander in Europe, Gen. Christopher Cavoli, told Congress in April that Russia had lost only about 10% of its fleet in Ukraine, indicating it had a lot left in its airpower arsenal.

NATO members are worried about the future threat from Russia, with many warning that Russia may attack another member in Europe if it's not defeated in Ukraine.

Members are ramping up defense spending and making more defense agreements with each other, with the ones closest to Russia boosting their border defenses .

"As this crisis goes on, the prospect of a general war against NATO becomes more real," Clarke said. "That's not to say that that's very likely, but it's at least a bit more likely than it was two years ago."

Russia's air force would probably lose in a direct engagement with NATO air forces, multiple experts have told BI, as NATO's combined airpower is much larger and more advanced. But Baum and other air-warfare experts have warned that Russia's air force shouldn't be underestimated and have cautioned that NATO should be ready.

Russia's air force is weaker than NATO's airpower, but Russia's war in Ukraine shows it can still cause a lot of damage. It adapts in devastating ways, as it has demonstrated with the guided-glide-bomb operations against Ukraine.

Peter Layton, a fellow at the Griffith Asia Institute who's a former Royal Australian Air Force officer, said Russia might very well have a future NATO conflict in mind as it makes decisions today.

For instance, he said, Russia might believe that in a war with NATO, its air forces could "survive long enough to counter some NATO air raids and help defend Russian ground forces for a short time." Such a plan would require not squandering assets in Ukraine. And Layton wasn't the only expert to share that assessment.

Russian considerations may, in turn, be shaping current combat conditions in the war in Ukraine. "NATO's power in the air is inhibiting the Russians from committing all of their air power, or more of it, to Ukraine," Clarke said.

He said Russia wanted to keep its air force looking strong as a weaker Russian air force would "weaken Putin's political hand in anything he then tries to do in relation to NATO politics." And, in a future conflict, Russia would want its air force to be powerful.

Ukraine is still downing Russian jets

The Ukrainian armed forces have a significantly smaller and older air force than Russia does. Its few jets are all Soviet-era, but Russia has one of the world's biggest air forces with many more modern combat aircraft.

But neither side has been particularly successful at changing the war from the air, considering the threat posed to aircraft by the proliferation of ground-based air-defense systems.

Experts in air warfare previously told BI that Ukraine's achievements here were remarkable and ones that may have stopped the war from quickly ending in a Russian victory.

Russia's losses are much higher than Ukraine's, though it has more to lose. According to a February update from the open-source intelligence site Oryx, Ukraine had lost at least 135 fixed and rotary-wing aircraft, while Russia had lost nearly double that figure .

Ukraine has claimed some big kill streaks shooting down Russian aircraft, including downing 10 jets in 10 days in February. Russia's air force often appears to back off after such victories .

Beyond fighter jets and fighter-bombers, Ukrainian forces have also downed some high-value Russian aircraft. This includes an A-50 command and control aircraft in January. The Russians have only a few of these planes available.

This prolific threat to anything flying could put Russia's advanced Su-57s at risk were they to fly combat missions over Ukraine. But avoiding the fight hasn't completely shielded the small Su-57 fleet. Ukraine managed to damage one in a long-range strike on an air base hundreds of miles inside Russian territory.

Holding its airpower back has largely protected the force, though. Layton said Russia had kept many aircraft out of Ukrainian airspace since "at least after the first few months." Russia's air force has suffered high attrition rates from Ukraine's ground-based air defenses when operating in the country.

Russian combat aircraft tend to use weapons that let them "generally stay safely inside Russian airspace while firing into Ukraine." Russia notably saw big aircraft losses in February when more of its jets came close to the front lines to support land forces by launching glide bombs, Layton said.

He said Russia "has a lot of trouble replacing lost advanced aircraft," making only a few a year. And sanctions from many countries against Russia for its invasion could make things more difficult, he said.

Clarke said that Russia could use its strategic bombers more effectively if they flew over Ukrainian territory but that "they've only got a certain number of strategic bombers, and if they lose eight or 10 of them, then that will put quite a hole in the force."

He said the environment in Ukraine was too "risky" for Russia's air force, especially if it wanted to maintain its force for a future fight.

Russia's comfortable losing what it's losing now

Curtis said Russia was using its most advanced assets in ways that kept them "completely safe," such as launching long-range attacks from inside Russia, adding that there was "effectively no risk."

And Layton said Russia might be motivated by its own weapons industry, which has ramped up but still faces challenges. "Any losses impact possible future export sales as Russian aircraft now appear less capable," he said. Some experts have suggested this as a possible reason for keeping the Su-57 out of the fight, especially given Russia's significant activity in foreign arms sales.

George Barros, a Russia analyst at the US's Institute for the Study of War think tank, which has been closely tracking the war, said Russia had only a small number of many of its most advanced aircraft, which means they wouldn't make a big difference if Russia was taking on NATO's air forces, though Russia has other capable platforms to supplement.

He said Russia had a propaganda reason for keeping them intact before any future conflict, one that even outweighed the effect they could have in Ukraine.

On the Su-57, he said that "if the Russians were to lose it, it would be just such an international embarrassment."

Western intelligence and aviation experts previously told BI's Jake Epstein that the absence of the Su-57 suggested Russia might not be confident in the jet and probably wanted to avoid any reputational damage that could come if any were shot down.

Gustav Gressel, an expert in Russian defense policy at the European Council on Foreign Relations, said that Russia had "very few" Su-57s and that "they are expensive to operate." Other jets could do the same jobs needed in Ukraine, he said, "and it would be less embarrassing if they would be shot down." Russia is understood to have only about 20 Su-57s in service .

Tim Robinson, a military-aviation specialist at the UK's Royal Aeronautical Society, said that Russia's Su-57s "are the high-quality assets, high expensive assets, stealth fighters" and that the Russians "don't want to lose them."

Experts have also pointed to Russian fears that if its most advanced jets were shot down over Ukraine-held territory, it would expose their most advanced technology and could be a windfall for Ukraine's Western partners.

Robinson said that if any Su-57s were shot down over Ukrainian-held territory, Western intelligence experts would get to "crawl all over it and find out its secret."

Baum said Russia's decisions on what goes into Ukraine and what doesn't might be "calculated." They might have decided "that they don't need to roll out their more sophisticated weapons yet or ramp up their sortie rate yet," he said.

Curtis said Russia was "happy to lose what it's using in Ukraine," adding, "in most instances, I'm afraid, that's people." Russia has been known for treating its soldiers as disposable, including by using what are described as "meat grinder" tactics , such as high-cost "human wave" assaults.

He said that for now, Russia could afford to keep its most advanced assets out of Ukraine as its strategy for victory wasn't by total military triumph. He said that instead, Russia was aiming to grind down Western appetite for helping Ukraine and exhaust Ukraine's support.

He said Russia is "not really going to be too fussed about how modern and how useful the capability" it gives its soldiers is.

The defense reporter Jake Epstein contributed to this reporting.