"either the pilot can designate it manually or it can be done with NCTR (you can see this in the Mig-21 shoot down video from Desert Storm - the plane is 'sniffed' as a Mig-21 and the box turns to a diamond
). With the simple system we have - diamond means enemy, box means friendly/unknown (because ED don't seem to have added the 'FRIEND' text yet)."
NCTR wont ID anything as Hostile or Friendly it may tell you what it thinks the aircraft type is but thats it. Consider if you have the same types on both sides .... NCTR doesn't know that