Working on getting it to run.
I noticed that the directory is named
Ja37 but the paths in the files are Aircraft/
ja37/...
The textures fuse.png and wing.png are named with capital first letter but in the ac-file they are not.
Same problem with for
Internal
Flame.xml and
External
Flame.xml
On windows this does not make any difference (if I remember correctly) but in other OS it does.
Maybe change the name of the aircraft directory? (As the name of the real aircraft is JA 37 I would suggest JA37 or Saab-JA37.)
A suggestion:
You do not have to give the Aircraft/ja37/ in the file path for the different files under the aircraft’s own directory, just the relative path in that directory (eg. Models/ja37-model.xml).
By only using the relative path you will make it easier to use the aircraft in different
FG configurations.
Edit: And PILOT.png that is named pilot.png in the xml