symbol of the rapid progress of development. According to aviation author Krzysztof Luto, the highly unusual decision to adopt jet engine propulsion for the prospective aircraft had been at the insistence of Soviet officials, who also actively participated in the design process. Accordingly, the design team were compelled to use such an engine due to political factors rather than practical ones. Recognising the favourable qualities of the An-2, it was decided to adopt some similar design features, such as its biplane configuration that gave favourable lift characteristics. Flight testing It was recognised from the onset that use of a jet engine for a relatively slow agricultural biplane posed several problems that would need to be addressed, including unforgiving handling and maintenance issues. In order to better explore these problems, an experimental airplane Lala-1, for ("Flying Laboratory 1"), was constructed in Poland. Performing its first flight on 10 February 1972, this aircraft comprised the whole forward section of an An-2, together with its wings, while the rear part was cut off and replaced with a frame construction that housed a single Ivchenko-Progress AI-25 turbofan engine (as used on the tri-engined Yakovlev Yak-40 and the single-engined Aero L-39 Albatros fighter-trainer). The Lala-1 was equipped with agricultural devices; experiences and data gathered from its test flights greatly influenced the design of the M-15. On 30 May 1973, the first variant of the M-15 conducted its maiden flight; it was followed by the second prototype on 9 January 1974. During the following years, both aircraft were intensively tested, and were joined by a pre-production series. Even at this stage of the project, the aircraft's performance was being criticised and constantly compared unfavourably with its An-2 predecessor. The M-15 was publicly displayed at the Paris Air Show of 1976; it has been claimed that it was at this event that the aircraft received its popular nickname of "Belphegor", a result of its strange appearance and noisy jet engine propulsion. Production During 1976, serial production of the M-15 commenced. At one stage, Soviet agriculture planners had intended to order as many as 3,000 aircraft to meet its needs; however, operations of the M-15 under real world circumstances proved to be a largely disappointing experience. As an inherent consequence of adopting a jet engine, it was not an economical aircraft to operate, being inferior in this aspect to the An-2 that the M-15 had been envisioned to