There were people that had actionable intelligence, but were prohibited by inter agency rules in getting the information to another agency that could actually do something about it. This has been in the news every since then. But chicken little always over reacts.
There were agencies that knew suspicious individuals were taking pilot lessons whose origins and background were known - but they were prohibited in telling another agency in the chain of information. There were actually alarms in several areas, but no communication. If any one agency had all the data, the over all picture would have been obvious. Osama and company's activities were well known by the CIA and foreign intelligence, but no one in country was allowed to gather any of that data either. Each of them had a piece of the picture but couldn't put two and two together without the over all view.
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