Zero type 21 is the main force of HNA in the early stage. Starting from zero type 21, ship hook and radio positioning equipment necessary for long-distance navigation are added to the tail of the aircraft. The lift of Japanese aircraft carrier is only slightly wider than the 12m wingspan of zero type-1, which is easy to damage the wing in case of transportation negligence; Considering the convenience of operation on the air bus is one of the key items that must be considered when designing the shipborne aircraft. The solution is to redesign the curved main wing ends on both sides to be able to fold up 50 cm manually, so as to facilitate shipborne operation. By 1942, Mitsubishi had produced 740 zero type 21 and Zhongdao had produced 2821. [8]