I dunno, 1 igla rocket sent a cobra down in flames yesterday for me (on normal). I was doing that while a buddy was manning the fixed AT missile at the antenna, with a couple more friends we held off multiple ground vehicles and a cobra with just infantry.
I've also knocked down a couple of helicopters as a tank machine gunner.
Tactics, tactics, tactics...
I might complain that the pilots getting a computer launch warning from an IR missile is BS- in reality only active emitters (radar, lasers) set off automated warnings. An IR-sensing (passive) guidance system doesn't set off anything except maybe the pilot seeing the smoke trail.