...isn't it FAA regulation to notify the air force when a plane's transponder goes off since like the 70's after the hostage crisis?
No, not to my knowledge. Transponders fail occassionally, some planes don't have them, and they are not required in all airspaces.
On 9/11, three of the four planes had their transponders turned off. It turns out, though, that the "root" problem was not the transponders, but the sluggishness of the system that was in place.
And it's not like these were stealth craft, just because their transponders went off they didn't vanish. Okay so there are 4000 other blips on screen... WITH transponders. Are you telling me they have no filters on their systems to track objects with no codes and screen out the rest?
ATC generally has the ability to look for "primary" radar returns (planes with no transponders), but it is not an easy process.
Also, not every radar can look everywhere. The right radar needs to be looking in the right direction.
But in the case of 9/11, all of this transponder/radar stuff was sort've a tertiary issue. (See below.)
Unlikely. They had a vector, they had a procedure, they had the means and the opportunity and still nothing happened. FOUR times in ONE day in less than what, three hours? I'm no George Noory but that stretches waaaaaaaay beyond coincidence OR incompetence for me.
NORAD did not have a vector.
The NORAD/FAA procedures were designed for typical hijackings, and they failed miserably in this case.
NORAD/FAA did have the means to intercept the airliners with fighters, but the system was unable to respond rapidly enough to make this happen.
NORAD never had a real opportunity to intervene on 9/11.
American Flight 11 - Departing Boston
8:14am - Hijacking began
8:25am - FAA determined the plane had been hijacked.
8:38am - NORAD was notified.
8:46am - 2 jets were scrambled from Massachussets (the closest "on alert"). But the AF didn't know where to send them. So they circled for six minutes.
8:46am - Flight 11 crashed into the North Tower.
United Flight 175 - Departing Boston
The same Controller was responsible for this flight as Flight 11. So, he was a bit distracted.
8:42am - Hijacking began (approximately).
8:55am - Controller determined that the aircraft was hijacked.
9:01am - NORAD was notified that this plane was hijacked. The two jets from Massachussets were still en route to the New York area.
9:03am - Flight 175 crashed into the South Tower.
American Flight 77 - Departing Dulles
8:51am - Hijacking began.
9:00am - ATC in Indianopolis realized there was a problem, but believed the plane had crashed. (They know nothing of the WTC events.)
9:20am - ATC-Indianopolis learned of the WTC events and the other hijackings. They began looking for the plane, but didn't find it until it was only about 40 miles from the Pentagon.
9:37am - Flight 77 crashes into the Pentagon. NORAD was never even notified about this hijacking. Langley AFB (near DC) had scrambled two jets at 9:30am but mistakenly sent them EAST.
United Flight 93 - Departing Newark
9:28am - Hijacking began.
9:32am - FAA determined this plane had been hijacked.
10:03am - Flight 93 crashed.
10:07am - NORAD was notified about this hijacking.
So, as you can see there is no suggestion of any kind've NORAD "stand down".
The 9/11 report notes that it was once suggested that NORAD not keep any aircraft on alert. As it was, on 9/11 there were only 14 aircraft on alert in the entire U.S.