I don't believe you can set icons to off. The best you can do is limit the range they turn on.
That's still a terrible idea. Getback, the next time a plane flies overhead look at it. Note how far it might be, 1000 feet? 5000 feet? A mile or more? Note that most times you can make out individual details such as windows, gear doors, flaps, control surfaces....
In-game you get 1 single pixel.
You're only introducing virtual blind-ness by trying to implement this. The icon system 1) makes up for a complete lack of pixel-based technology to replicate what the human eye can see, and 2) simulates a ground control center that would be tracking all friendlies (you see a wing of fighters, call in, and they say "those are friendlies" or "those are enemies").
Icons are there for a reason. I have tried flying mini-missions with all icons off, and you can't tell the difference between a P-51B and a 109G2 until you're at 250 yards in this game, basically. I almost shot down a wingman. Historically? I've have known who it was instantly, and from further out. WW2 pilots could even read the fuselage codes and know which of their wingmen was in trouble. Try doing THAT in this game past 100 yards.
