It is not a 'sophisticated' attack. The operation planner did a masterful job of keeping to the KISS principle -- Keep It Simple, Sh!thead -- and the openness of American society made it easy for him.
Once an airliner, or any aircraft for that matter, is airborne, the captain is 'The Law'. His orders are supreme. The environment demands such a status. There is no one to help the aircraft and its occupants. If anything bad happen, the observers can only watch helplessly. The aircraft is truly independent of any manmade laws. Communication can be suspended and ground orders disobeyed. The pilot can fly his ship anywhere and anyhow he likes. Air traffic controllers are not in control, they can only give instructions and hope they will be taken seriously precisely because of the wish to remain alive safely by the aircrew and their passengers. With this understanding, it become easy to see how such an operation like 9/11 can be planned and executed.
In any military operation that involve discrete units working towards a common goal, it is desirable to have each unit to be as
AUTONOMOUS as possible, perhaps even each can have its own plan. If we take each airliner as a discrete operation for a takeover and finally a weapon, we can see, with the above understanding of how air travel works, that there is no need for each unit to be in communication with each other. The only goal and order for the crews is to have the attack on so-and-so day, perhaps in the AM or PM. What is there to 'coordinate' when the target, the WTC complex, is immobile, highly visible and not defended against air attacks? There is not even a need to give the crews a set day. Just make it a requirement that all air attacks, from hijackings to crashing into the targets, occur on the same day, as close to each other as possible. Let the crews work out among themselves on who attack which ground target. If not Sept 11, then perhaps Oct 8 or around Thanksgiving Day holiday when air travel schedules are important to people. So it could be that Sept 11, 2001 was the day that all crews were confident that they would have the greatest odds of success. Osama bin Laden does not need to be in constant contact to 'coordinate' anything.
The argument that NORAD was ordered to 'stand down' or that the US military could have shot down any hijacked airliner is utterly absurd once the nature and mission of NORAD is known. The North American Aerospace Defense (NORAD) Command is a joint US-Canada military operation whose mission is to look
BEYOND the borders. By law NORAD have
NO jurisdiction inside US airspace. The proper authority over civilan airspace is the Federal Aviation Administration (FAA). Only the FAA can call upon the US military for assistance. NORAD does not have legal imprimatur to act on its own. US military personnel are forbidden by law to make formal arrests.
http://www.dtic.mil/doctrine/jel/cjcsd/cjcsi/3610_01a.pdf
Prior to Sept 11, 2001, air traffic controllers have the understanding that airline hijackings are mainly political statements with the hijackers
WANTING TO REMAIN ALIVE to make their case to the media. If there is a hijacking in progress, the controller who has airspace jurisdiction which involve the aircraft in question would immediately call or 'squawk' code 7500 for an air piracy in progress, clear the immediate airspace and remain in contact with the aircraft to guide it to the nearest airport. On Sept 11, 2001 this understanding was not abandoned and the procedures to deal with a hijacking was followed as best as humanly possible. There were no procedures to deal with the possibility that the hijackers were suicidal and therefore refused to communicate with ground controllers.
As for the argument that NORAD was supposed to 'scrambled' armed fighters the moment any airliner deviate from its file flight plan --
STOOOPPPIIIIDDD. If a captain has a sick passenger or an expectant mother ready to deliver her baby, he has the authority to declare an In-Flight Emergency (IFE), which is mainly an FYI to ground controllers, and
IMMEDIATELY deviate from his fligh plan, which is filed by his airline anyway. Wealthy capitalists with their private jets deviate from file flight plans with regular frequency. How is the USAF supposed to 'scrambled' any armed fighter yo make an intercept? How many fighter bases must the US have in every state within 5 minutes flight time to make any interceptions? Would that make the US pretty much a dictatorship? If so, then why bother with so free an air travel system anyway? How about recreational aviation like powered gliders or light homemade aircrafts? Best to do make them illegal so that the USAF would not have to make so much interceptions of suspicious radar echoes.
This is why the '9/11 Truth' movement is slowly dying an embarrassing death.