This is at least the second such incident reported, as another was brought down by Russia's S400 defense system in early January. If it was the Su-35 they're very expensive (around $85mil USD) and Russia does not have many of them.

Source: National Interest

The Kremlin may have lost another Su-35 aircraft on Thursday, and the Su-27 derivative may have been the victim of friendly fire according to early reports. Video of a Russian fighter aircraft engulfed in flames as it fell back to the earth quickly circulated on social media.

Mikhail Razvozhayev, the Russian-imposed governor of Sevastopol announced via the social messaging Telegram that the pilot had safely ejected, and was subsequently rescued after landing about 200 meters from the shore.

"A military plane fell into the sea… Civilian objects were not damaged," Razvozhayev wrote.

Multiple reports identified the aircraft as a Su-35 (NATO reporting name "Flanker-E"). If it is confirmed that the aircraft was a Su-35, it would be at least the seventh Flanker-E lost in Ukraine and the third downed this year. The first Su-35 was shot down over Eastern Ukraine on February 17, while two days later a second was shot down over the Azov Sea.

There have also been reports that the Russian aircraft lost on Thursday was mistakenly shot down by Russian anti-aircraft defense. This would be the second such Su-35 aircraft to fall victim to friendly fire, after another was targeted by a Russian S-400 air defense system in early January near Krasnoperekopsk, a town in the northern part of the Crimean peninsula. That damaged Su-35 was able to successfully land at a military airfield near occupied Melitopol in the Zaporizhzhia region.

As always, a soundtrack added by Ukrainians.