However, on 21 October 1937, Petlyakov was arrested together with Tupolev and the entire directorate of the TsAGI on trumped-up charges of sabotage, espionage and of aiding the Russian Fascist Party. Many of his colleagues were executed. In 1939 he was moved from a prison to an NKVD "sharashka" for aircraft designers near Moscow, where many ex-TsAGI people had already been sent to work. Petlyakov was given the task of designing a high-altitude fighter, which he successfully accomplished. However, operational experience in the Soviet-Finnish War of 1939-1940 showed that this was not what the Soviet Air Force needed, and Lavrentiy Beria, head of the NKVD and of the "sharashka" system, ordered that the fighter be redesigned as a dive bomber, with the promise that Petlyakov and his colleagues would be released on its successful completion.