JoeCrip,
Listen dude, "Relax, it's just a game."

I have had this happen to me as well, and I have also done it a number of time, more on the side of a mistake. I would rather conserve ammo than shoot down a plane that is going down.
I distinctly remember two instances when I "stole" a kill. Once, when I was a newbie, I wanted to make sure the buff was going down. Second, I was so intent in getting the kill, I failed to notice that the enemy was floating, probably more due to lag.
When it did happen to me, the Spit was half winged obviously about to lose control. However, in the furball, 5 or 6 guys decided to go after it anyway.
But so what? Can't you enjoy the game without getting a kill? Resorting to multiple check 6 calls and then justifying it here... well... you are no different from the guy who took your kills.
Relax, it's just a game. Don't let getting kills the only source of your enjoyment in the game.