History is filled with people who dug their own graves while a person with a gun pointed at them told them to do it.
It takes an exceptional person to act before their fate is sealed and the majority of passengers, if not all of them, will be in a state of denial or shock at the situation they are in preventing them from action. Others who might want to act, but not having been in the situation before, will think about what to do or when the right moment to act is, and the right moment will never come, especially if the hijackers can guarantee the first person who acts dies.
Prior to 9/11, hijackings occurred with mild frequency and the official policy was appeasement: get the plane safely landed and then negotiate with the hijackers. In any ways, 9/11 was possible due to exploiting that particular policy.
Since 9/11 there have been attempts to disrupt planes and no shortage of people willing to tackle the person responsible.
As a frequent flyer who has thought about this scenario a bit, I agree with this. And I actually think that as long as the FAs kept making their inane announcements about credit cards and so forth, most pax wouldn't even notice a takeover at the front of the plane.
You do what the person with the gun says, because you believe they'll shoot if you don't. If you believe that they will shoot and kill you regardless, following their orders is (at best) going to give you a few more agonizing minutes to live. The threat becomes meaningless.
Don't try to overpower the hijackers? You die. Try to overpower the hijackers and fail? You die. Try to overpower the hijackers and succeed? You live. It only takes one person to do the math and realize they are basically in a no-loss scenario.
Yes, the math is the easy part, doing is the hard part. The difference between understanding and doing is large and denial, shock, rumination, and rationalization all fuel inaction and there is often a moment in which it becomes too late.
People on death marches, in concentration camps, or other similar scenarios have the same math, and yet they get gassed or forced to dig their own graves after which they are shot and buried in them.
So yes, rationally that all makes sense and we should celebrate anyone putting themselves at risk to fight for the benefit of a larger group, but reality is different, especially if the hijackers can guarantee at least one death.
To say a hijack could never happen again is wrong. The doors are a much more reasonable explanation than the courage of men.
History also gets forgotten, such as the history of secret police or mass deportation efforts as is quite clear in this thread.
Assuming something is true doesn't make it true. Colluding airport employees as well as rural airports seem like clear vulnerabilities. When thinking about security problems you don't just assume your security measure always succeed and assuming that all passengers are "equal" seems like a poor assumption, especially for an exceptional case by highly motivated people, potentially with state backing.
Why are we accepting this even at airport?
Locking the doors of the cockpit made another 9/11 close to impossible.