Three Japanese warbirds are available at the Aircraft page of this site. These aircraft are not Mac OS X specific so you can use these on any platform (as long as it runs FlightGear, of course) since these are not a part of FlightGear Mac OS X but a part of FlightGear itself.
Currently available Japanese warbirds are:
- A6M2 Zero Fighter
- J7W Shinden
- Ki-84 Hayate