The Americans acknowledged that the Russian Su-57 fighter jet is superior to the American F-35.
The claim about the Su-57 fighter was made in one American journal. The journal in question, Military Watch, is hardly ever quoted anywhere but in Russia.
According to the Insider, there is no substantial background information about who owns and runs Military Watch. The journal's editor seems to have an author’s profile, which is now empty, on the strongly Kremlin-loyal English language outlet Russia Insider. euvsdisinfo.eu/antisemitism-and-pro-kremlin-propaganda/,
Further debunking: theins.ru/antifake/107509,