The Sukhoi Su-27 heavy air superiority fighter - codenamed 'Flanker' by NATO - was designed during the Cold War as a Soviet counter to potential Western opponents such as the US Air Force's F-15 Eagle. It first flew in 1977. Service entry began during 1985, and when the 'Flanker' started appearing at Western air displays in the hands of Sukhoi test pilots, starting at Paris in 1989, it astounded spectators with its manoeuvrability. In the post-Soviet era, the original Su-27 series has continued to equip the Russian armed forces, and carried on serving with the Ukrainian Air Force as well as other former Soviet states and several export customers. The design has continued to be developed for both Russia and overseas markets, some of the latest derivatives incorporating thrust vectoring. The Ukrainian Su-27s (one P model and one UB model) that are coming to Fairford for RIAT 2018 are on the strength of the 831st Tactical Aviation Brigade, based at Myrhorod in central Ukraine.