Starting with 1948, Romania tailored its military to Soviet concepts and doctrine. On February 15, 1949, the Aviation Command was established based on the Soviet model (regiments instead of flotillas). New Soviet aircraft, such as Yakovlev Yak-18, Polikarpov Po-2, Lavochkin La-9, Tupolev Tu-2, and Ilyushin Il-10 entered service. A year later, 9 Yakovlev Yak-17s and Yak-23s entered the air force, and in 1952, other 88 aircraft: MiG-15 and MiG-17. In 1958, the first supersonic fighter MiG-19 entered the inventory. Three years later, in February 1962, a new fighter was added to the inventory, MiG-21, which represented one of the most effective fighters of that time.