registration number 68001 a pre-production Tu-144, number 77101 nine production Tu-144S, numbers 77102 to 77110 five Tu-144D models, numbers 77111 to 77115. Although its last commercial passenger flight was in 1978, production of the Tu-144 did not cease until 1983, when construction of the airframe was stopped and left partially complete. The last production aircraft, Tu-144D number 77116, was not completed and was left derelict for many years on Voronezh East airfield. There was at least one ground test airframe for static testing in parallel with the development of prototype 68001. Operational history Operational service The Tu-144S went into service on 26 December 1975, flying mail and freight between Moscow and Alma-Ata in preparation for passenger services, which commenced on 1 November 1977. The type certificate was issued by the USSR Gosaviaregister on 29 October 1977. The passenger service ran a semi-scheduled service until the first Tu-144D experienced an in-flight failure during a pre-delivery test flight, crash-landing on 23 May 1978 with two crew fatalities. The Tu-144's 55th and last scheduled passenger flight occurred on 1 June 1978. An Aeroflot freight-only service recommenced using the new production variant Tu-144D ("D" for Dal'nyaya – "long range") aircraft on 23 June 1979, including longer routes from Moscow to Khabarovsk made possible by the more efficient Kolesov RD-36-51 turbojet engines, which also increased the maximum cruising speed to Mach 2.15. There were only 103 scheduled flights before the Tu-144 was removed from commercial service. Later use The Tu-144 programme was cancelled by a Soviet government decree on 1 July 1983 that also provided for future use of the remaining Tu-144 aircraft as airborne laboratories. In 1985, Tu-144D were used to train pilots for the Soviet Buran space shuttle. In 1986–1988 Tu-144D No. 77114, built in 1981, was used for medical and biological research of high-altitude atmosphere radiological conditions. Further research was planned but not completed, due to lack of funding. Use by NASA In the early 1990s, a wealthy businesswoman, Judith DePaul, and her company IBP Aerospace negotiated an agreement with Tupolev, NASA, Rockwell and later Boeing. They offered a Tu-144 as a testbed for NASA's High Speed Commercial Research program, which was intended to design a second-generation supersonic jetliner called the High Speed Civil Transport. In 1995, Tu-144D No. 77114 (with only 82.5 hours of flight time) was taken out of storage and after extensive modification at a cost of US$350million, designated