I believe that some branch of the military uses the term "terrestrial" to distinguish either from at-sea or in-the-air. That's a vague recollection from someone I know (and I forget who) with a military background using the term that way, and me going "huh?" and either getting or deriving an explanation.

Anyway, assuming that I'm not completely pulling that out of thin air, it's possible that "non-terrestrial officers" could be a perfectly ordinary term to refer to officers serving on a naval vessel at sea, or officers who regularly fly planes.