On 3 September 1939, France and the United Kingdom declared war on Germany. On 17 November, the French Government and Czechoslovak National Liberation Committee agreed that Czechoslovak airmen would be transferred from the Foreign Legion to the French Air Force pending the formation of a Czechoslovak air force. Kuttelwascher was one of about 100 who were sent to the fighter training base at Chartres Aerodrome, where he quickly learnt to fly the Morane-Saulnier M.S.406C.1 fighter. However, he was not transferred to a combat squadron until 17 May 1940, when he was assigned to Groupe de Chasse III/3 at Beauvais–Tillé.