The situation for planes is analogous, as the plane could be NOE or outside the radar ring. I doubt you want 100% information in a game like this.
MH
NOE is extremely difficult these days because the altitude required to keep under the bar dar is VERY low. True, GVs cannot fly any lower than they do already and hence there is no NOE equivalent. For this reason I proposed in previous discussions that there will be a delay between the spawn and the bar dar count - that is, a new GV that spawned is "under" the radar for X minutes, which gives a GV "NOE" mission time to advance away from the spawn and spread out before their presence in the sector is announced.
That's for survivability (and it's not enough). If you try GVing, you will see that in AH with experienced players attack aircraft, left alone, kill the GV every time. Kind of like if you (an adult) picked a fight with a 6-year-old. Of course there are exceptions to every rule, but this *is* the rule.
This situation is also analogous to what happens with planes. A single plane can also be easily overwhelmed by enemy fighters. A group of GVs with wirbles and perhaps even <gasp> fighter cover is not so vulnerable to attackers - quite the opposite, the Stukas, 410s, IL2s and A20s are vulnerable to fighters and wirbles. Not to mention the ease at which a single bomber can shut down the ords by precision bombing from 20k. In almost all cases when there is a massive GV attack, the ords are disabled on the base. Taking out GVs with cannons is a risky business. Unless HTC gives me the Mossie XVIII with the 57mm Mollins AP cannon. Then I will not care about ords.
What would happen in WWII if some enemy tank wandered on its own and spotted 2 km from a fighter-bombers base? I can tell you what happened in real life when a group of terrorist, due to a navigational error, landed from the sea 2 km near a base of attack helicopters. That is also analogous.