Organization of the Imperial Japanese Navy Air Service

A kōkūtai in the broadest terms could comprise a flight and base element of either a carrier or land-based air group.

In terms of the flight element, it was generally composed of 18 to 27 aircraft and took the name of the carrier or air station where it was originally formed.

The non-flight element of kōkūtai was composed of ground units that provided aircraft maintenance and air base service functions.

[6] The air groups and stations outside those ports were placed under the command of the nearest naval base (chinjufu).

Just as the aircraft and flight crew on board a Japanese carrier or a seaplane tender were made an integral part of a ships complement, when land-based or shore-based (seaplane) air units were formed, the bases at which they were stationed were seen as equivalent of the ships of the carrier-based hikōtai formed a part of.

While regulations establishing land-based air groups were set forth in 1916 and 1919, it was not until the early 1930s that a series of regulations and instructions set forth the specific internal organizations of air groups, their locations, functions, and their training, though these changed from time to time right up to the end of the Pacific War.

Standing combined air groups (jōsetsu rengō kōkutai), intended to be more permanent, were established in December 1938.

[7] As the war in the Pacific progressed, this structure lacked flexibility and hampered front-line operations, consequently, in March 1944 the IJN's land-based air forces were restructured, and certain hikōtai were given independent numerical designations and an identity of their own outside the parent Kōkūtai.

[5] Buntai was the smallest administrative unit of aviation personnel, as opposed to tactical or operational formations of aircraft.

[1] It was commanded by a Buntaichō and was made up of the required number of personnel necessary to fly and maintain one chutai, which typically consisted nine aircraft.

[5] The number of personnel in a buntai would vary, depending on the mission or role of the unit and type of aircraft that it operated.

Each new design was first given an experimental Shi number, based upon the current Japanese imperial year of reign.