The Sukhoi Su-35S Flanker E is a highly modified and improved derivative of the Su-27. In the 1980s modifications were made to the Su-27 (Su-27M) also referred to as Su-35. About 20 years later a heavily modified member of the Flanker family was produced and given the title of Su-35S Flanker E. Considered by many to be the most capable fourth generation fighter in the sky and equipped with many fifth generation technologies. This probably will be the last of the Flanker family when the fifth generation Russian aircraft arrive.
In 2015 Russia sent armaments as well as Sukhoi Su-25, Su-24M bombers, Su-34 and Su-30SM aircraft to Syria to prop up the Syrian Government against Syrian opposition militant groups trying to depose the President. In 2018 Russia sent their new Su-35s to increase their firepower and support the other aircraft on their missions. Russia saw this as a way to test the Su-35 in real conflict conditions as well as an opportunity to show the world these aircraft and hopefully to obtain purchase orders from other countries.