Shortly before 9/11, the NSA also intercepted multiple phone calls from Bin Laden's chief of operations to the United States.
The CIA and the NSA had been intercepting phone calls by the hijackers for years.
Indeed, two days before 9/11, Osama Bin Laden called his stepmother and told her "In two days, you're going to hear big news and you're not going to hear from me for a while.” US officials later told CNN that “in recent years they've been able to monitor some of bin Laden's telephone communications with his [step]mother. Bin Laden at the time was using a satellite telephone, and the signals were intercepted and sometimes recorded." Indeed, before 9/11, to impress important visitors, NSA analysts would occasionally play audio tapes of bin Laden talking to his stepmother.
9/11 family member and "Jersey Girl" Patty Casazza was told by whistleblowers that -- before 9/11 -- the government knew the exact day, the type of attack, and the targets.
The Military Had Drilled for Attacks Such as 9/11
Indeed, the military had actually drilled for aerial attacks with planes:
The North American Aerospace Defense Command (NORAD), the military air defense agency responsible for protecting the U.S. mainland, had run drills for several years of planes being used as weapons against the World Trade Center and other U.S. high-profile buildings, and "numerous types of civilian and military aircraft were used as mock hijacked aircraft". In other words, drills using REAL AIRCRAFT simulating terrorist attacks crashing jets into buildings, including the twin towers, were run.
And the military had conducted numerous drills of planes crashing into the Pentagon. For example, see this official military website showing a military drill conducted in 2000 using miniatures; this article concerning a May 2001 exercise of a plane crashing into the Pentagon (see also this article and this one); and this article about yet another drill of a plane hitting the Pentagon from August 2001.
(Indeed, many of the drills appear to have included warning alarms and evacuation of the building.)
The military had also run war games involving multiple, simultaneous hijackings (first paragraph), so this aspect of 9/11 was not as overwhelming as we have been led to believe.
See this short excerpt of a Peter Jennings newscast on 9/11 (excuse the music and subtitles).
There are literally hundreds of further examples of facts which tend to show that 9/11 was foreseeable (see this timeline for additional information).
But What Do High-Level Officials Say?
In addition to the former CIA director and other credible witnesses discussed above, many high-level officials have gone on record raising questions concerning the foreseeability of the attacks:
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