How do you discernate among ground targets FROM an aircraft?
It doesn't look as if much ground-IFF systems were on the field today (but maybe I'm wrong), and if they are or when they'll be, they tend to be more related to ground-to-ground weapons, AT helos at most.
There is no way for a strike aircraft to pick out friendly ground units with IFF, except probably radar stations. IFF is by definition air-to-air and ground-to-air only, because only aircrafts have transponders.
Only way is proper recognition training
, and that comes with country training I guess, although you can add experince to your pilots if you like.
Anyway, friendly fire from aircraft IS quite frequent rhight now, some happened during OIF/OEF, and way back in the first Gulf War.
Besides, you must take into account the sped of the aircraft and the time scale involved. One turn is about 3 to 5 minutes. You send a plane strike at one hex, from one direction, and he comes 2 turns (max 10 min.) later, an 500 mph or so, and, tough luck, some of your units are on his way.
Your pilot has about a half minute visibility on the target, probably already programmed the bombing run, what do you expect him to do?
Would you prefer your own planes to break off at the first doubt? Under fire?
Now you will agree that you don't see any friendly fire AGAINST aircrafts, which would be less likely, but can happen.
Anyway, the game has NO friendly fire logic AFAIK, and I don't think one is planned. Aircrafts are just instructed to deal with one target hex, more than often they don't see an enemy unit at all, particularly bombers, and just drop all they have on the target spot and don't give a damn.
On the other hand, you can decrease your chances of friendly fire by carefully planning your entry routes according to where your ground forces are, and always better target a unit that is in someone's sight, and not too close from your forces.
In desperate cases, I guess you could try to raise vision, FC and experience of modern fighters, that may be helpful (?).
Cheers,
Plasma