- The draw order of the airplane is determined by the object types - glass is drawn last to avoid translucency artifacts.
- Interior light from the plane is only spilled on the "inside" objects.
- Glass objects are excluded from shadow calculations to avoid having opaque windows in the airplane shadow.
In particular, you should have glass for the airplane windows in an attached object tagged as type 'glass'; do not attach your glass to the cockpit object, which cannot be categorized as glass. If you have an old plane with glass in the cockpit, consider cutting the object in half in a 3-d editor and attaching the glass separately.
(You should also use our prop disc animation, rather than use an OBJ for prop discs; the OBJ format doesn't contain the z-buffer tricks necessary to make the prop look right.)