succeed. In contrast, the M-15 could only achieve a range of 215 nautical miles, half that of the An-2, largely due to its jet engine and relatively high weight. Maintenance was also more intensive, a factor which was compounded by the typically austere nature of agricultural airstrips. The aircraft was also expensive, both to construct and to operate. Furthermore, pilots would commonly need additional training for handling jet-powered aircraft, which was a further complication for any transition to the M-15. Production of the aircraft was terminated without ceremony during 1981, by which point only 175 aircraft had been completed. The M-15 was only ever operated inside the USSR, despite the type having been made available to potential export customers. Taking its envisioned role was the preexisting An-2, which continued to be used in the agricultural role into the twenty-first century. Of those M-15s that were produced, very few remained operational by 1995, its operators having rarely found the aircraft to be satisfactory. It is believed that the M-15 is the world's only jet agricultural aircraft (i.e., the world's only jet cropduster), as well as the world's only jet biplane and the world's slowest jet aircraft, at least amongst aircraft that have been put in mass production. Design The PZL M-15 Belphegor was a metal twin-boom sesquiplane. It was intended to be routinely operated by a single pilot, but also had provisions for two additional crew to serve as technicians when deemed necessary. Portions of the lower wings and the chemicals tanks were composed of a laminate to avoid corrosion. The upper and lower wings were connected with two thick columns which housed the chemical tanks. It was outfitted with a fixed tricycle landing gear arrangement. The M-15 was a relatively heavy aircraft, and has been described as being the heaviest biplane to ever be produced. For the crop-dusting mission, the M-15 could accommodate a payload of just under three tons of pesticides within two sizable pylons that separated its two wings; chemical dispersal was achieved via compressed air. This storage system was relatively unorthodox, the conventional An-2 simply stored these in a single tank housed within the fuselage in a space that could be reused for various other cargoes if not fitted. As such, the arrangement adopted upon the M-15 allowed for no such flexibility and severely limited alternative uses for the aircraft. To avoid the engine exhaust interfering with