US aviation officials failed to respond to dozens of warnings of a possible terrorist threat months before September 11th, 2001, according to a previously undisclosed report by the panel that examined the attacks.
The report, which was recently declassified, said federal aviation officials reviewed 52 intelligence reports between April 1st, 2001, and September 10th, 2001, that warned about Osama bin Laden or al-Qaeda.
Most of the intelligence summaries created by the Federal Aviation Administration's (FAA) security branch dealt with overseas threats, the document said.
It noted there was no evidence the FAA knew of a plot to hijack commercial planes in the United States to use as weapons.
"Nevertheless the FAA had indeed considered the possibility that terrorists would hijack a plane and use it as a weapon," said the August 2004 staff report, which gave more details on what the FAA knew than were included in the September 11th commission's overall report released in July.
The staff report, not officially released but censored and given to the National Archives, criticised the FAA for failing to take steps to deter the attacks.
It said FAA officials had enough information to hold classified briefings between March 2001 and May 2001 at 19 of the busiest US airports to warn of the danger of an attack, including bin Laden's threats against aviation.
The agency also distributed an unclassified CD-ROM presentation to air carriers and airports citing the possibility terrorists might conduct suicide hijackings but saying "fortunately we have no indication that any group is currently thinking in that direction." The CD-ROM briefings said a domestic hijacking would be difficult.
"We don't rule it out. . . . If however, the intent of the hijacker is not to exchange hostages for prisoners, but to commit suicide in a spectacular explosion, a domestic hijacking would probably be preferable," the report cited the CD-ROM as saying.