Yes that attack was viable for less than 1 hour. On flight 93 the passenger revolt began at 9:57AM, and the the first plane hit the World Trade Center at 9:01AM

Yes that attack was viable for less than 1 hour. On flight 93 the passenger revolt began at 9:57AM, and the the first plane hit the World Trade Center at 9:01AM [1] https://en.m.wikipedia.org/wiki/United_Airlines_Flight_93 https://en.m.wikipedia.org/wiki/United_Airlines_Flight_93 > After the hijackers took control of the plane, several passengers and flight attendants learned from phone calls that suicide attacks had already been made by hijacked airliners on the World Trade Center in New York City and the Pentagon in Arlington County, Virginia. Many of the passengers then attempted to regain control of the aircraft from the hijackers. During the struggle, the plane crashed into a field near a reclaimed strip mine in Stonycreek Township And if that hadn’t worked, before the crash the military was already authorized to shoot down that flight. So the system adapted quickly.