With the start of the Second Sino-Japanese War, there was a tremendous need for air transport capability by the Japanese military, which had traditionally drawn on the resources of the civilian national flag carrier, Japan Air Transport, for its charter requirements. As Japan Air Transport’s capacity was limited, conflict arose between the Imperial Japanese Army and Imperial Japanese Navy over priority, and the government saw the need for the creation of a single, national monopoly. The government bought a 50 percent share of Japan Air Transport, and renamed it the Dai Nippon Kōkū in December 1938. After the start of 1942, the airline became completely government-owned.
With the start of the Pacific War in December 1941, the Japanese government suspended all commercial operations, and the airline was requisitioned for use only in military operations. Operations continued until the surrender of Japan in August 1945, despite heavy losses. During the Allied occupation, surviving aircraft and equipment were confiscated, and civil aviation in Japan was banned until the formation of Japan Air Lines in 1951.