Pilots from the Imperial Japanese Army Air Force Academy at the completion of a 2,175-mile (3,500-kilometer) flight cooperation study that flew around the mainland of Japan. Their Tachikawa Ki-9 (Allied code name "Spruce") intermediate trainers are behind them. The flight was heavily promoted and the press greeted them at landing. 2,615 Ki-9s were built from 1934 to 1945. Unlike the United States, which built an extensive pilot training program at the outbreak of the war, Japan never created a massive training program, preferring to use prewar procedures. After the Battle of Midway, Japanese pilot losses were never replaced because of the long time it took to train pilots and a lack of aviation fuel for training. Haneda Airport was a civilian field before the war, but was militarized when hostilities began to defend Tokyo. Built on a man-made island, it is the primary domestic airport for Japan.