I've shot up many a plane, only to have someone else get the kill.
I've blown through formations, drained my guns without popping any of them, only to be flying home minding my own business and rack up Kill messages as someone else pops them off.
Bottom line is, if They did enough damage to the plane to begin with, then the best you could hope for is an Assist.
Fly, try to be fair, but you can't cover everyones 6, give everyone check 6 calls, or be aware of every single person that may be angling for every single plane. Enjoy the game and squelch the griefers, lifes too short.