Sasebo/Omura location of 21st Naval Air Arsenal (Dai-nijuichi Kaigun Kokusho), which from 1941 built aircraft to established designs: 25 Aichi B7A2, 103 Mitsubishi A5M4-K trainers (to Arsenal’s design), 236 A6M2-K trainers (also to Sasebo design) and 590 Mitsubishi F1M2 seaplanes.