The PZL M-15 was a jet-powered sesquiplane designed and manufactured by the Polish aircraft company WSK PZL-Mielec for agricultural aviation. In reference to both its strange looks and relatively loud jet engine, the aircraft was nicknamed Belphegor, after the noisy demon. Development of the M-15 can be traced back to a Soviet requirement for a modern agricultural aircraft to succeed the Antonov An-2; it was at the insistence of Soviet officials that jet propulsion would power the type. WSK Mielec's design team recognised the value of the An-2's biplane configuration to the role and set about developing an initial experimental aircraft, the Lala-1, for ("Flying Laboratory 1") to explore the use of a jet engine with such a configuration. On 20 May 1973, the first M-15 prototype performed its maiden flight; even during the test flight phase, it was apparent that there were several drawbacks to the aircraft, including its poor handling, limited range, and high operating costs. While production commenced in 1976, these problems remained unresolved and meant that the M-15 was noticeably inferior in several respects to the An-2. During 1981, production was terminated in favour of procuring more An-2s; a total of 175 M-15s were built against the many thousands which had once been planned. Development Origins By 1970, the Soviet Union was formulating a new requirement for an agricultural aircraft that it intended to use above the very large areas of Soviet farms, the kolkhoz collectives, and state-owned sovkhoz. It was explicitly stated in the requirement that the envisioned aircraft was to be both more efficient and modern than the existing Antonov An-2SKh and An-2R, of which tens of thousands had been produced primarily to perform this role. During 1971, following an agreement between the Soviet Union and Poland on the matter, the Polish aircraft manufacturer WSK Mielec set about developing its own original response to the requirement. By this point, Poland had already produced the agricultural Antonov An-2R under licence for export back to the USSR, while agricultural planes had become a Polish specialization within the Comecon. WSK Mielec's design team was headed by two engineers, Kazimierz Gocyła and Riamir Izmailov. The designers recognised that it would be highly desirable to retain many of the characteristics of the successful An-2, while also improving upon them where feasible. As such, there was a reported desire to incorporate state-of-the-art technologies and to make the aircraft into a