I'd like you to read this from a former ATC that I interviewed. This is not my interview, but his account of 9/11 is exactly the same.
He says the events of 9/11, particularly the non-response of NORAD and air-traffic controllers is not possible without intervention and that turning off a planes responder does not mean that plane is lost to contollers or the military.
"In addition to my career as an Air Traffic Controller, I have a great deal of other experience in aviation. I was a Certified Commercial Pilot and accumulated 1600 hours total time in light aircraft; qualified in Single-Engine Land, Multi-Engine Land, Single-Engine Sea, and Glider. I was also a Certified Flight Instructor and Certified Ground Instructor. And prior to my becoming an Air Traffic Controller, I passed the Flight Engineer Basic exam focused on the Boeing 727 and accumulated over 2000 hours of aircraft maintenance, repair and rebuilding time.
I knew within hours of the attacks on 9/11/2001 that it was an inside job. Based on my 11-year experience as an FAA Air Traffic Controller in the busy Northeast corridor, including hundreds of hours of training, briefings, air refuelings, low altitude bombing drills, being part of huge military exercises, daily military training exercises, interacting on a routine basis directly with NORAD radar personnel, and based on my own direct experience dealing with in-flight emergency situations, including two instances of hijacked commercial airliners, I state unequivocally; There is absolutely no way that four large commercial airliners could have flown around off course for 30 to 60 minutes on 9/11 without being intercepted and shot completely out of the sky by our jet fighters unless very highly placed people in our government and our military wanted it to happen.
It is important for people to understand that scrambling jet fighters to intercept aircraft showing the signs of experiencing “IN-FLIGHT EMERGENCIES” such as going off course without authorization, losing a transponder signal and/or losing radio contact is a common and routine task executed jointly between the FAA and NORAD controllers. The entire “national defense-first responder” intercept system has many highly-trained civilian and military personnel who are committed and well-trained to this task. FAA and NORAD continuously monitor our skies and fighter planes and pilots are on the ready 24/7 to handle these situations. Jet fighters typically intercept any suspect plane over the United States within 10 - 15 minutes of notification of a problem.
This type of "immediate, high speed, high priority and emergency" scramble had been happening regularly approximately 75 - 150 times per year for ten years. In the same ten years, there were ZERO "low speed, delayed reaction, and low priority" hijacking scrambles reported, which means that the only time interceptors were ever scrambled for ten years before 9/11, they were using the high speed immediate scrambles. The system was well tuned and ready before June 2001. However, the "emergency scramble" is NOT what was used on 9/11/2001...it was the "laissez fair" scramble for a hijacking that had to get Pentagon approval before departing…and there was none forthcoming."
http://www.communitycurrency.org/robin.html
His reference to June 2001 references the Stand-Down Order I talked about.