How about something from the Senate Intelligence Committee as quoted in here the Village Voice? This would corroborate the story don't you think?   Any reason to doubt the Senate Intelligence Committee?

"In April 2000, according to the Senate Intelligence Committee report of September 2002, a 'walk-in' source appeared at the FBI's Newark office and told agents he had been to a training camp in Pakistan and there learned hijacking techniques and received arms training. The man said he was to rendezvous with five or six other people in the U.S. to participate in a plot that involved hijacking a plane and flying it to Afghanistan. There were to be pilots among the group. If the mission aborted, then the plane would be blown up. The walk-in passed an FBI polygraph, but the agency was never able to verify the story. So said the Senate report. That apparently was the end of it."

Who Knew?