Wikipedia has a nice list of hijackings dating from 1950-2010.
Might be a good idea to review some of those listed that were done with guns.
I'd think there has been enough to warrant our current 'no cc' on plane gunlaws.
We can't just focus on the tactics/reasons used on 9-11, but rather the entire history of hijackings and what weapons were used in ALL of them.
Heck, I'd be happy if they let me take my pocketknife on the plane again.
There were some done with knives too.