The Sukhoi Su-35 (Russian: Сухой Су-35; NATO reporting name: Flanker-E) is the designation for two improved derivatives of the Su-27 air-defence fighter. They are single-seat, twin-engine, supermaneuverable aircraft, designed by the Sukhoi Design Bureau and built by the Komsomolsk-on-Amur Aircraft Plant. The first variant was designed by the Soviet Union during the 1980s as an improvement on the Su-27 and was known as the Su-27M. This derivative incorporated canards and a multi-function radar that transformed the aircraft into a multi-role aircraft, which was structurally reinforced to cope with its greater weight. The first prototype made its maiden flight in June 1988. As the aircraft was not mass-produced due to the dissolution of the Soviet Union, Sukhoi re-designated the aircraft as Su-35 to attract export orders. The fourteen aircraft produced were used for tests and demonstrations; one example had thrust-vectoring engines and the resultant Su-37 was used as a technology demonstrator. A sole Su-35UB two-seat trainer was also built in the late 1990s that resembled the Su-30MK family. In 2003, Sukhoi embarked on a second modernization of the Su-27 to serve as an interim aircraft awaiting the development of the Sukhoi PAK FA (Su-57) program. Also known as Su-35, this version has a redesigned cockpit and weapons-control system compared to the Su-27M and features thrust-vectoring engines in place of the canards. The type made its first flight in February 2008; although the aircraft was designed for export, the Russian Air Force in 2009 became the launch customer of the aircraft, with the production version called Su-35S. China's People's Liberation Army Air Force and the Indonesian Air Force have also ordered the aircraft.