In 1966, the Japan Air Self-Defense Force transport fleet was composed primarily of Curtiss C-46 Commandos, a retired midwar American design built in large numbers before the end of World War II. While relatively capable for its time, the C-46 did not fare well in comparison to newer aircraft such as the Lockheed C-130 Hercules, and the JASDF therefore elected to replace it with a domestically-designed and -manufactured transport aircraft.
For this purpose, they turned to the Nihon Aircraft Manufacturing Corporation, a consortium of several major corporations, which had begun to produce commercially its YS-11 airliner four years earlier. NAMC decided that Kawasaki Heavy Industries was to be the prime contractor, and the airplane thus bears that company's name. The aircraft has been used as military transport for the JASDF since its maiden flight in November 1970.
Japanese policies at the time on military equipment were strict in that they were not to have offensive capabilities, and so the maximum range was cut in order to keep the aircraft's operational range inside Japan. This proved to be a problem after Okinawa was returned to Japan from the US, and the aircraft had trouble reaching the island from distant areas. Thus production was reduced and the C-130 was introduced.
- XC-1: Prototypes.
- C-1/C-1A: Medium-range military transport version.
The last five C-1s ordered were fitted with an additional 4,730 litre fuel tank.
- EC-1: EW training aircraft.
- C-1FTB: Flight test bed used for testing various equipment.
- Asuka/QSTOL: Quiet STOL research aircraft, developed by the National Aerospace Laboratory.
Powered by four FRJ710 turbofan engines and making use of the Coanda effect. It was built to research STOL using upper surface blowing, aircraft noise reduction, fly-by-wire systems and composite materials construction. The only example built is currently on display in Kakamigahara Museum in Gifu, Japan.