It was designed by the French aircraft manufacturer SNCASE during the early 1950s, who were keen to exploit the potential advantages of a mixed-power propulsion system.

While SNCASE did opt to submit their design for evaluation towards satisfying this requirement, the more conventional Fiat G.91 was picked as the competition's winner instead, subsequently being manufactured in quantity for numerous nations.

[2] According to author Michel van Pelt, French Air Force officials were against a pure rocket-powered fight, akin to the wartime-era Messerschmitt Me 163 Komet, but instead favoured a mixed-propulsion approach, using a combination of rocket and turbojet engines.

During 1944, a new company, Société d'Etudes pour la Propulsion par Réaction (SEPR), was founded for the purpose of developing France's own domestic rocket engines.

[4] The design team produced a compact aircraft furnished with a 60° delta wing and powered by a single SNECMA Atar 101F turbojet engine, equipped with afterburning.

[1] According to aviation author Michel van Pelt, the limited missile armament of only one AA.20 was a major point of criticism of the Durandal, and contributed to its cancellation.

[4] A pair of prototype aircraft were constructed; on 20 April 1956, the first performed its maiden flight at Istres, initially flying only using jet power, the rocket motor was not installed at all.