Like Lusche said in your other thread, there is a bug in the kill/death list.
Someone else may have filled the plane with rounds 15 minutes BEFORE you even saw him. Your rounds just pushed him over the edge. That is one of the reasons people will only fly cannon birds. Blast past a plane and put some rounds in him and run away. If you stay alive long enough someone else will finish him off and you'll get the kill.
