First flight was on 1 April 1939 and combat trials were concluded in July 1940 with 15 pre-production A6M2's sent to two squadrons by the end of the month. These aircraft had folding wing tips to accommodate aircraft carrier elevators, and were the ones first seen by Gen. Chennault in China, and at Pearl Harbor in December 1941. Although the A6M2 met or exceeded original design specifications, modifications were taking place at the Mitsubishi factory to improve roll rate, speed up handling aboard carriers, and utilize the uprated Sakae 21, 1,130 hp engine. The first A6M3 type 32 (code named HAMP) took to the air on 15 July 1941 with production beginning in April 42. A total of 343 aircraft were produced by August 43, when the type 52 A6M5 began production.