Russia is scared to fly its best jets over Ukraine in case they're shot down and NATO gets hold of the wreckage, expert says

• Russia is holding back on using its advanced Su-57s over Ukrainian airspace, UK intel said Monday.
• An expert explained why to Insider: Russia fears the consequences of losing one.

Russia is avoiding flying its advanced combat jets over Ukraine for fear of the wreckage from a crash giving away the plane's secrets, an expert told Insider.

The Sukhoi Su-57, a modern Russian aircraft prized for its stealth, has not been a regular feature of the war so far, despite Moscow's efforts to hype its capabilities.

It has been used in the conflict— per an intelligence update earlier this week from the British defense ministry — but only from within Russian airspace.

Per the British update, Russia sends the jets up and has them fire long-range missiles at targets in Ukraine. But it won't risk sending them over the border, where Ukrainian air defenses could knock them out.

Justin Bronk spoke to Insider about why Russia made that call. Bronk is an airpower & technology expert with the Royal United Services Institute (RUSI) think tank in London.

Bronk told Insider that Russia is scared of the consequences if a Su-57 was shot down and Ukraine's allies in NATO could study the wreckage.

These partners "would certainly be very interested to know more about" some of the jet's unique features, he said. In particular, he highlighted its "innovative radar arrangement" as of particular interest.

The UK update said Russia was holding back with Su-57s because it was "avoiding the reputational damage, reduced export prospects, and the compromise of sensitive technology which would come from any loss" of the craft.

Bronk agreed that a crash over Ukraine would be "extremely embarrassing" for Russia "because it would expose the stealth as really not being particularly effective."

Russia's defense minister, Sergei Shoigu, said in August that the jet had performed "brilliantly" in the invasion, boasting about its features.

"The aircraft has a very high degree of protection against various air defense systems, has protection against missiles. There is a lot of stuff there. Most importantly, it has very powerful weapons," he said, per state media.

Russia's tactic of using the jets from its own territory is indicative of its continued risk-averse approach to employing its air force in the war against Ukraine.

"They're being very cautious with their entire combat aircraft fleet, and despite that, they continue to take a steady trickle of losses," Bronk told Insider.

"So the fear of losses to a degree where technology is compromised has certainly caused the Russians to be pretty cautious across the board."