Spare Squadron, officially the 444th Fighter Squadron, is a penal military unit in the Osean Air Defense Force. The unit is comprised of Osean military personnel who have committed some form of crime. Members of this squadron are referred to as prisoners and are considered expendable by the Osean Defense Forces.
The squadron had no standardized aircraft, but all planes were decorated with 'sin lines' on the tails in the form of white dashes blocking out previous unit decals. The number of marks depended on the severity of the crime committed.
Spare Squadron was deployed during the Lighthouse War, the extent of which is currently unknown.
- The number 4 is considered an unlucky number in Japan; it can be pronounced "shi", which shares the same pronunciation for death (死).