The Severest of penalties, and I dont mean points, should be leveled on those who broke the rules. This has to stop. And it is getting worse with the growing population, as Sled pointed out in Last nights, State of the FSO address.
It's not just the upping the second fighter that is wrong, but when this happens, escpecially in large numbers, the whole Frame is FUBAR. There is no way to accurately measure and penalize, the impact these illegal planes are having across the battlefield. It's more than kills and deaths, as there can be numerous consequential outcomes due directly to these infractions.
Bad form, and a big Boo to the violaters.
EDIT: I would add, I bet the vast majority here would prefer playing with 400 guys and gals following the rules, then 500 with people running amok and soiling the Operation.