The prototype of Russia's legendary Su-27 fighter jet, T-10 (Sukhoi's 10th design) first flew in May 1977. After serious redesigns the T-10 evolved into the definitive Su-27 configuration, which entered service with the Soviet Air Forces in 1985. Starting in 2004, the Russian Air Force began a major update of the original Soviet Su-27 fleet. The upgraded variants were designated Su-27SM, which belong to the 4+ generation. See the images of Russia's iconic fighter jet in this photo gallery.