The Yakovlev Yak-9 was a single-engine fighter aircraft used by the Soviet Union in World War II and after. It was the most numerous Soviet fighter of the war and remained in production from 1942 to 1948, with 16,769 built. Yak-9DD were used primarily to escort Petlyakov Pe-2 and Tupolev Tu-2 bombers although they proved less than ideal for this role due to insufficient speed advantage over the bombers. In 1944, several Yak-9DD were used to escort B-17 Flying Fortress and B-24 Liberator bombers attacking targets in Romania using the Ukraine-Romania-Italy routes.