While doing some searching I came across this website dated May 18, 2002. I thought some of this was interesting so I decided to share. If it's a repeat, I apologize now ahead of time.
<snip>
The last comment—“Within the American intelligence community, the warnings were taken seriously”—is crucial. It clearly indicates that in response to the ECHELON warnings, the entire U.S. intelligence community—all U.S. intelligence agencies—were on alert for a Project Bojinka-style attack, and consequently intensified surveillance. The New Yorker further reports that according to Richard A. Clarke, U.S. National Coordinator for Counterterrorism in the White House, about ten weeks before 11th September, the U.S. intelligence community was convinced that a terrorist attack by Al-Qaeda on U.S. soil was imminent. Seven to eight weeks prior to the 11th September attacks, all internal U.S. security agencies were warned of an impending Al-Qaeda attack against the Untied States that would likely occur in several weeks time. This warning coincided with the second ECHELON warning cited before:
“Meanwhile, intelligence had been streaming in concerning a likely Al Qaeda attack. ‘It all came together in the third week in June,’ Clarke said. ‘The C.I.A.’s view was that a major terrorist attack was coming in the next several weeks.’ On July 5th, Clarke summoned all the domestic security agencies—the Federal Aviation Administration, the Coast Guard, Customs, the Immigration and Naturalization Service, and the F.B.I.—and told them to increase their security in light of an impending attack.”<19>
It is apparent then that all U.S. intelligence agencies were fully expecting an impending attack by Al-Qaeda by the beginning of July 2001, and moreover that the U.S. intelligence community was aware that “terrorists were planning to hijack commercial aircraft to use as weapons to attack important symbols of American… culture.” In other words, the U.S. intelligence community was anticipating a Project Bojinka-style attack. Among the buildings identified as “symbolic of American culture” in Al-Qaeda’s Project Bojinka plans, known by U.S. intelligence, was the World Trade Center. That the WTC was an extremely likely target is further clear from the fact that operatives linked to Osama bin Laden had previously targeted the Twin Towers in a failed bombing attempt. As a consequence, the entire domestic intelligence and security apparatus seems to have been alerted to increase relevant security and surveillance.
Much more here...
http://www.mediamonitors.net/mosaddeq36.html