https://www.key.aero/article/uk-mod-claims-russia-using-su-57-ukraine-conflict?

The UK Ministry of Defence (MOD) has claimed that the Russian Aerospace Forces (RuASF) have “almost certainly” been using fifth-generation Sukhoi Su-57 multi-role fighters in combat missions against Ukraine for at least seven months.

The claim was first highlighted in the UK MOD’s daily defence intelligence update on the ongoing conflict in Ukraine on January 9, which stated that the Su-57 has been supporting the Russian war effort against Ukraine from afar since June 2022. The update was also one of the rare times that the Su-57’s unconfirmed NATO reporting name, Felon, has been used in describing the aircraft by a NATO member state.