Whacker: I take it you don't fly online all that much?
We call it kill stealing and it's sort of a blight on some online matches. I've observed the AI closely and they behave like humans up to a certain point after which they are much more fair. If the enemy aircraft has initiated the bailout or if the pilot is dead the AI will stop firing and ignore the plane. They will also ignore if there is a wing or the entire tail section is missing.
Otherwise they continue to shoot.
To some degree this "bug" is a historically and very human type response. The bigger problem isn't really the AI doing this but the scoring involved and that's where the game part of this comes in. It would be nice to share points relative to the amount of damage that one aircraft has dealt to another aircraft. So the magic BB for the steal is no longer a problem.