sid its not always friendly fire that kills teammates most are rams. So if a friendly flys in youre plane it can count as friendly kill against you.
That's not been my experience Zeno.
To be awarded a 'Friendly Kill' in the stats, you have to put a bullet into them before their aircraft is listed as disabled, if they manage to land and finish flight the 'Friendly Kill' won't count (you would still be guilty of friendly fire though).
If two friendlies collide, a 'Friendly Kill' would only be counted if one of them had put a bullet in the other first, certainly if a friendly flies in to your aircraft it will not count as a 'Friendly Kill' against you.
I accept the odd 'Friendly Kill' is almost inevitable on a 'Fast Action Server', occasionally you've already fired when a unseen friendly dives down through your bullet stream (you were possibly unseen by them as well) for example, but note, many players go a whole tour without a single 'Friendly kill'.
If we have to put numbers on it, I would define 1 'Friendly kill' in 100 'Air Kills' or 1% to be acceptable, even stretching that to 2% or 3% to provide a margin of error, but we already have some on 6% or 7% and these guys are all experienced players. That to me just indicates a person so wrapped up in his own score, he doesn't give a **** for his fellow players.
I'm being lenient at the moment, the server's still new and I'm still playing around with the settings, but the time will come when I will ban anyone with high 'Friendly Kill' stats for the benefit of the majority of the other players who don't seem to have a problem controlling friendly fire. I suggest now is a good time for these guys to start practicing a little discipline and care with their shots, it's not just about climbing to the top of the leaderboard quickest!