Yeah, positioned properly, they could have taken out quite a few, especially if they new who else had weapons and had the element of surprise and a hostage in front of them. I doubt even 25% of the passengers would be armed.
But sort of interesting—
I'll give you 25% carry rate among airline pax on and before 9/11.
Flight 93, 9 out of 38.
Flight 175, 14 out of 56.
Flight 77, 14 out of 58.
Flight 11, 20 out of 81.
Not including crew.
Just to help your argument, let's cut those in half. Now only 1 in 8 are packing.
Thought experiment: assuming that the other passengers don't get suspicious of you as you move from your assigned to your preferred seats, thus retaining the element of surprise, where do you and your three teammates position yourselves so that, when you jump up and either take a hostage or start shooting, none of the 4 to 10 armed passengers can keep you from taking control of the aircraft?
(Remember that the actions of the unarmed on Flight 93 prevented the accomplishment of the terrorists’ mission.)
After 9-11, I don't think a hijacking will succeed on an aircraft with a predominately American passenger roster with or without guns; and in the event our COTUS 2A rights were restored to the extent postulated on this thread, a good deal more than 25% of the pax would be packin’.