The project was authorized on 20 May 1954, parallel to the development of the Burya missile. The development however, began in April 1953 as a rocket-aircraft system by Myasishchev OKB with internal designation M-40.[3] The project was canceled in November 1957, when two prototypes were just ready for flight testing, in favor of the R-7 Semyorka, since ICBMs were considered unstoppable. Like the Burya, the Buran consisted of two stages, the booster rockets designated M-41, and the cruise missile stage designated M-42.[citation needed]