o None of the four jetliners were intercepted or shot down, with the exception of Flight 93, which was apparently shot down in spite of indications that passengers had regained control. Commentators speculated that the plotters intended for Flight 93 to crash into the Capitol building or the White House, but its downing in Pennsylvania was likely planned to provide heroic drama.
The apparently flawless execution of the attack is consistent with a sophisticated military operation and not with a kamakazi attack by ragtag bands of Islamic terrorists. Contrary to common assumptions, such a military operation did not require a wide-ranging conspiracy within the US military, but only of a small number of top-level officials. This is the case because of the nature of military command structures and extent of computer automation in US military systems.
First consider the structure of the military. Of all human institutions, military organizations are some of the most hierarchical and opaque ever devised. Military personnel are trained to follow orders without question, and to maintain strict secrecy about operations. Violations of codes of secrecy are strictly punished. More important, military personnel are typically directed on a need-to-know basis. Operatives are briefed only on facts necessary to the execution of their task. By dividing up a mission into sufficiently small tasks and delegating the tasks to different operatives, it is possible to execute the mission while preventing any individual operatives from seeing much of the larger picture. Such compartmentalization is an essential feature of the US military and intelligence agencies. In the execution of the 9/11/01 attack, even stricter compartmentalization and secrecy could have been practiced without that being apparent to operatives following orders.
Then consider how automation could have reduced the manpower requirements of the attack. Each of the principal tasks required to execute the attack were likely facilitated through computer automation.
* The takeovers of the jetliners may have been accomplished by hacking into the flight control computers. Their highly accurate attack maneuvers were likely achieved through pre-programming of their flight paths.
* The prevention of fighter intercepts may have been accomplished, in part, through the (automated) insertion of spurious radar blips in FAA and NORAD flight tracking systems.
* The controlled demolitions of the WTC towers were likely accomplished through the use of charges whose detonations were controlled by computer via radio links.
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