The first flight took place on 4th February 1934, under the specification Ka-14 The first mission of the aircraft was in September 1937 against China and later against the USA, during the Japanese attack on Pearl Harbour in December 1941. 788 aircraft were built by Mitsubishi, 303 additional by Watanabe and 264 by Omura under license. The performance of the A5M exceeded all the requirements. While 305 km/h was the required top speed, the A5M reached 405 km/h during a test flight.