In the middle of 1920s our army had two main fighter planes – Letov Š-20 and Avia BH-21. Both manufacturers offered a trainer aircraft, which featured the main fuselage of the production aircraft, but with reduced weight and weaker engine Škoda HS 8Aa. Those trainers were Letov Š-21 and Avia BH-22 respectively. In the end, the army chose Avia, while Š-21 was produced in only two examples. The first Š-21 had a three-colour camouflage and was completely destroyed when its pilot Andrej Beneš couldn’t pull it out of the spin. The pilot survived thanks to the plane’s metal frame. Letov didn’t give up and built a second prototype (marked again as Š-21.1).
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