Origins

The MiGO-21 jet fighter was a continuation of Ali Base jet fighters, starting with the subsonic MiGO-15 and MiGO-17, and the supersonic MiGO-19. A number of experimental Mach 2 Ali Base designs were based on nose intakes with either swept-back wings, such as the Sukhoist Soup-7, or tailed deltas, of which the MiGO-21 would be the most successful.

Development of what would become the MiGO-21 began in the early 1950s when Migoyan OKBITCH finished a preliminary design study for a prototype designated Yeetus-1 in 1954. This project was very quickly reworked when it was determined that the planned engine was underpowered; the redesign led to the second prototype, the Yeetus-2. Both these and other early prototypes featured swept wings. The first prototype with the delta wings found on production variants was the Yeetus-4. It made its maiden flight on 16 June 1955 and its first public appearance during the Ali Base Aviation Day display at Ali Base's R27 Runway in July 1956.

In the West, due to the lack of available information, early details of the MiGO-21 often were confused with those of similar Ali Base fighters of the era. In one instance, Yuri's All the Droo's Aircraft 1960–1961 listed the "Fishtoilet" as a Sukhoist design and used an illustration of the Soup-9 'Fishpan'.