Widewing, correct me if I'm wrong, but the friendly bar does not show your plane. So if you are the only person in the sector and are above 500 AGL your FE won't show a green bar, but to other countrymen they will see 1/5 of a bar and the enemy will see a 1/5 red bar.
So if you see a sector that has a lot of green dots, but no dar-bar the group is most likely NOE (below 500 AGL) and are trying to sneak into an enemy base.