According to Voice of America, Moscow has deployed two of its fifth generation Su-57 stealth fighter aircraft to Syria. The deployment was confirmed via satellite imagery circulated two Su-57s on the apron at Hmeymim Air Base in Syria. 

The U.S. Defence Department on Thursday declined to confirm the deployment of Russia's newest stealth jets to Syria, however, Russia did not deny the allegations and has yet to confirm the information. Russian news outlet Kommersant quoted military sources as saying that the Russian fifth-generation Su-57 fighter jets were deployed to Syria to test radar systems and electronic warfare and that aircraft will not take part in combat missions.