There is already a "fix" for this that has been coded into the game. Whoever does the majority of damage up to the point that critical damage awards a kill (the point at which the wing fell off in your AAR) is the pilot that gets the kill. After that point you can stack damage on the plane until it explodes and the kill will not be awarded to anyone else.
So, obviously someone had already caused all the damage needed and your shooting just wasn't enough to claim the kill.
Pretty sure shooting half a wing off isn't considered critical damage in this sense. Same with an engine kill or a PW even though both are likely to result in a kill. Lots of people land or ditch planes with half a wing missing. Some planes like the F6F are pretty easy to land with half of *each* wing missing if nobody finishes you off. Shooting a whole wing or the whole tail off is critical damage. So is setting someone on fire, you can pump a bazillion rounds into a burning plane and it won't change who gets the kill (though it may actually blow the plane up sooner if he's trying to ditch or still trying to kill someone else). Not sure about shooting just the vertical stab off but I *think* that is not critical damage for this purpose in the programming.
And putting rounds into an aircraft with no visible damage who is not currently being shot at is not kill stealing no matter how many rounds someone else as put in him before or after. The error in your statement is "someone had already caused all the damage needed". If they had caused all the damage needed, the wing would already have been off. It wasn't, ergo they had not caused ALL of the needed damage, they had caused MOST of the needed damage.
Kill stealing is irritating but not NEARLY as irritating is someone diving into your bullet stream out of nowhere with no warning so you killshoot yourself.
