When it comes to perks, I think it means when a plane represents a vast majority in the number of kills thereby becoming the "plane of choice" for the majority of the arena, that plane has unbalanced the arena and is then perked. The spit16 while a pretty darn good plane, dose NOT have a vase majority of kills each month. It may have the most, but not by much which means other planes still are competing with it. So it doesn't "unbalance" the arena.