What counts as a kill?
It seems rather inconsistent. Twice today in Career mode, I shot down a plane and saw parts of it break away, and subsequently a fireball on the ground, and I was not credited any kill. My pilot even radioed in that he destroyed his target.
Then a few times I shot just the radiator of an enemy plane, and 5 minutes later, I get credited a kill.
What's the criteria of a kill in this game?