To save time in developing a bomber of their own, the Soviet Union obtained three Boeing B-29 Superfortress bombers from the USAF in 1944, dismantled and analyzed them and began making a copy in 1945. Designated the Tu-4, an initial pre-production order for 20 was placed for the Soviet Air Force. Some compromises were made in quality of materials and systems and US engines were replaced by four Soviet 2400hp Ash-73TK engines. First flight was on 3rd July 1947, but the aircraft suffered severe and prolonged problems with all systems. 2805103 coded '01' is the sole survivor and is currently preserved at the Air Forces Red Banner Academy Museum, Monino, near Moscow where it can be seen on display.