Seems to me that if an entire wing or both elevators, or the tail have been shot off, then there ought to be code to prevent the possibility of kill stealing, which I presume at this stage there isn't. The plane that shoots off a wing or elevators, or tail, should automatically be locked in the system as the one that caused the catastrophic damage and be awarded the kill, even if a dozen others shoot at falling wreckage. Maybe the time delays on the internet prevent that, I don't know.
Shared-kills
If the first plane only shot off an aileron and one elevator of an enemy, and a second plane shot off the other aileron and the other elevator of the enemy, then there could be "shared" kills like WWII. No one gets an entire kill, and for simplicity, you might only break down to a half-shared kill and one third-shared kill. The first one, two or three that cause damage get kill points.