What would flying Bish have to do with it?
Bishops are country 1(or "0", internally), it's the first country
Many of us have experienced a very small glitch over the years that when you log into the arena, you sometimes (rarely) see exactly one line of Bish country chat, despite being rook or knight. It's that split second at login where the server tries to determine on which country you are really on.
I can
imagine that something similar might be happening to the AI plane as well. Player discos, and when the server takes over the plane there's a split second where the country of that AI drone is determined. So if a Bish pilot hits the AI drone at that very moment, the server might think a Bish is shootign at a Bish.
But that's just a guess that came to my mind