Or if passengers were still allowed to carry knives.
I've logged a lot of miles, always carried a 3.5" locking pocket knife in my pocket. Always razor-sharp, was never stopped. It accompanied me on every flight I've ever had, including the disarmed state of Great Britain, and the formerly-communist Romania. Nobody ever said "boo" to me about it, and I insisted on being armed, even though it's a small comfort.
Had other passengers felt the same way, and actively carried knives... The events of 9/11 would NOT have transpired. This is not a claim that I could have single-handedly stopped all the terrorists on a given plane (quite unlikely, actually), but these fanatics never would have succeeded against an entire plane armed and opposing them, no matter how fanatical they were. There would have simply been 19 dead loons, that's all...
Arm the pilots, arm all the passengers.
A well-armed society, is a polite society, you know???