the Shuttle. Even though the Molniya Scientific Production Association proposed its Spiral program design (halted 13 years earlier), it was rejected as being altogether dissimilar from the American shuttle design. The construction of the shuttles began in 1980, and by 1984 the first full-scale Buran was rolled out. The first suborbital test flight of a scale-model (BOR-5) took place as early as July 1983. As the project progressed, five additional scale-model flights were performed. A test vehicle was constructed with four jet engines mounted at the rear; this vehicle is usually referred to as OK-GLI, or as the "Buran aerodynamic analogue". The jets were used to take off from a normal landing strip, and once it reached a designated point, the engines were cut and OK-GLI glided back to land. This provided invaluable information about the handling characteristics of the Buran design, and significantly differed from the carrier plane/air drop method used by the United States and the test craft. Twenty-four test flights of OK-GLI were performed by the Gromov Flight Research Institute test pilots and researchers after which the shuttle was "worn out". The developers considered using a couple of Mil Mi-26 helicopters to "bundle" lift the Buran, but test flights with a mock-up showed how risky and impractical that was. The VM-T ferried components and the Antonov An-225 Mriya (the heaviest airplane ever) was designed and used to ferry the shuttle. The flight and ground-testing software also required research. In 1983 the Buran developers estimated that the software development would require several thousand programmers if done with their existing methodology (in assembly language), and they appealed to Keldysh Institute of Applied Mathematics for assistance. It was decided to develop a new high-level "problem-oriented" programming language. Researchers at Keldysh developed two languages: PROL2 (used for real-time programming of onboard systems) and DIPOL (used for the ground-based test systems), as well as the development and debugging environment SAPO PROLOGUE. There was also an operating system known as Prolog Manager. Work on these languages continued beyond the end of the Buran program, with PROL2 being extended into SIPROL, and eventually all three languages developed into DRAKON which is still in use in the Russian space industry. A declassified May 1990 CIA report citing open-source intelligence material states that the software for the Buran spacecraft was written in "the French-developed programming language known as Prolog", possibly due to confusion with the name