The "scramble Vs intercept" is often brought up in response to the "many intercepts" figure, but it is a very misleading response.
The 67 in the months prior to 9/11 (I think it was 6 months, not a year) should be considered intercepts, giving CTers the benefit of the doubt.
However...
NORAD's area of responsibility is the Air Defence Identification Zone - or ADIZ. This is a "buffer" zone located over water at the edges of the USA.
You can see the Continental US ADIZ here.
It is defined by Federal Aviation Regulation Part 99 section 43:
Intercepts inside the ADIZ are, and always have been, routine. There is standard proceedure for these intercepts.
However, the 9/11 attacks did not involve aircraft operating inside the ADIZ. They were domestic flights over CONUS (Continential United States) airspace. Prior to 9/11 there was NO standard intercept proceedure for flights inside CONUS. Standard hijacking proceedure was to notify the FAA and hand over control to the FBI. As a domestic crime, only the FBI had the authority to request military support.
So the question that should be asked is:
Did NORAD perform any successful intercepts inside CONUS Airspace prior to 9/11?
The answer is yes. In the decade prior to 9/11 NORAD was involved in ONE intercept.
This was October 25th, 1999. The aircraft was N47BA - a Learjet35 owned by Payne Stewart.
The NTSB report on this incident is here.
So how well did NORAD do on this occasion?
Well, first off, some basic comparisons:
1) N47BA did not deviate from its intended flightplan.
2) The transponder onboard N47BA remained on at all times throughout the intercept.
Neither of the above is true of the 9/11 flights. This make intercept many magnitudes more difficult.
So then, how well did NORAD do?
The first intercept aircraft - a test pilot from the 40th Flight Test Squadron at Eglin AFB, Florida, reached N47BA 81 minutes after communication was lost.
So let's compare that to the flights of 9/11, and total flight duration of those aircraft:
FLIGHT HIJACKING CRASH DURATION
AA11 0813 0846 33 minutes
UA175 0847 0903 16 minutes
AA77 0856 0937 41 minutes
UA93 0928 1003 35 minutes
So the intercept of N47BA - an aircraft with transponder functioning and in straight level flight - took almost TWICE AS LONG as the longest flight duration on 9/11 - that of AA77.
The facts speak for themselves. A successful intercept of any of the 9/11 flights was impossible.
-Gumboot
ETA.
It is worth noting that the times I gave are from the moment of hijacking. Of more relevance is the "window of opportunity" - the time between when NORAD were notified of a hijacking and when that flight crashed. On 9/11 the longest window of opportunity that NORAD would receive was 9 minutes for AA11. The N47BA intercept took 9 times as long.
