Tu-104 into passenger service before satisfactory stability and controllability had been achieved. During high-altitude and high-speed flight the aircraft was prone to longitudinal instability, and also at high altitudes, it had a narrow range of angle of attack separating the aircraft from stalls known as coffin corner. These problems created the preconditions for spin dives, that happened twice before the Tu-104 was eventually properly tested and the problem was resolved. This politically motivated rush, along with the fact that the project was essentially ideologically motivated rather than driven by intrinsic needs of the Soviet society, and with general technological insufficiencies of Soviet industrial base, contributed to the final undoing of the Tu-144 project. (Alexander Poukhov, one of the Tu-144 design engineers who subsequently rose to be one of the bureau's senior designers, estimated in 1998 that the Tu-144 project was 10–15 years beyond the USSR's capabilities at that time). Moon suggests that subordination of available Soviet R&D resource allocation to the Tu-144 programme significantly slowed down the development of other Soviet aircraft projects, such as the Il-86 wide-body jet, and stagnated Soviet aviation development for almost a decade. After project cancellation After ceasing the Tu-144 programme, Tu-144D No. 77114 (aircraft 101 or 08-2) carried out test flights between the 13–20 July 1983 to establish 13 world records registered with the Fédération Aéronautique Internationale (FAI). These records established an altitude of with a range of loads up to 30 tonnes, and a sustained speed of over a closed circuit of up to with similar loads. To put the numbers in perspective, Concorde's service ceiling under a typical Transatlantic flight payload of 10 tonnes is , and this is higher than the record set by the Tu-144D. According to unverified sources, during a 26 March 1974 test flight a Concorde reached its maximum speed ever of (Mach 2.23) at an altitude of , and during subsequent test flights reached maximum altitude of . It is unclear why Tu-144D's maximum achievable altitude would be lower than Concorde's even regular flight altitude, given that Tupolev's data claim better lift-to-drag ratio for the Tu-144 (over 8.0 for Tu-144D vs Concorde's 7.3–7.7 at Mach 2.x) and the thrust of the Tu-144D's RD-36-51 engines is higher than Concorde's Olympus 593 engines. Concorde was originally designed for cruising speeds up to Mach 2.2, but its regular service speed was limited to Mach 2.02 to reduce fuel consumption, extend