With Germany on the retreat during the final years of World War II, production began in Czechoslovakia of the venerable Bf 109 fighter at the Avia factory in Prague-Akovice with sub-assembly taking place in several other small factories. However, only a small number had been delivered by the end of the war yet production continued anyway under the new designation S.199. Due to the lack of stocks of native DB 605 engines (lost during a fire), it was decided to substitute them for Jumo 211s from uncompleted He 111 bombers. Unfortunately, this new engine was completely unsuitable for a fighter: it gave too much torque at high power (especially during takeoffs), was difficult to land, and had extremely poor handling leading to the unflattering nickname 'Mezec' (Mule). Nevertheless, the S.199s claim to fame was in being the first fighter obtained for the Israeli Air Force where it was also universally disliked but used with some success in the 1948 Arab-Israeli War.

The original S.99 was basically a Czech built version of the Bf 109G-14 (as well as a two seater, the CS.99, based on the G-12) which entered very limited service with Czech forces during the final year of the war. First flight of the S.199 with Jumo 211 engines took place on 25 March 1947 and was followed by a two-seat CS.199 trainer less than two years later.