LOL Sandman, I bet some one is going to tell u that the entire responsability is in the shooting plane. So, once you have your victim centered in your sight, you better keep a look at all directions to be sure no friendly plane is overpassing you by dead six or below (be sure to roll 180 degrees also to check that)
It has been discused over and over in the past, and it is really funny to see how the people is happy with this feature. It is even funnier to see how some ones try to justify it.
I suppose it was developed in an attempt to "educate" the newbies that keep at your six shooting through your plane trying to score some hits in the enemy at your 12. But the most common effect is just yours experience because, once "ducated" these newbies learnt to overpass you trying to steal your kill and forcing yourself to stop shooting or be killed.