No passenger plane has been hijacked since then, because terrorists know the passengers will not allow it.

Passengers became a herd that morning, and the lesson was learned by everyone.

I'm less confident in this than you are.

9/11 was 21 years ago. Most young men weren't alive/don't remember it/didn't experience it be they were young children.

I would think it's a lot harder to find a brave man in a random crowd in 2022 rather than 2001.

The boys and men who witnessed 9/11 are now middle-aged and seniors.