Some interesting reading here...The Intelligence Community's Knowledge of the September 11 Hijackers Prior to September 11, 2001
The CIA employee told us that he had, at the time, been assigned to work at the FBI Strategic Information Operations Center to fix problems "in communicating between the CIA and the FBI." His e-mail, however, makes no mention of the CIA's determination that al-Mihdhar held a U.S. multiple-entry visa.
What a failure SIOC was. And who was in charge? Check it out.
And check this out...John O'Neill was an F.B.I. agent with an obsession: the growing threat of Al Qaeda.
Bodine denied his application to reënter the country. She refuses to discuss that decision. "Too much is being made of John O'Neill's being in Yemen or not," she told me. "John O'Neill did not discover Al Qaeda. He did not discover Osama bin Laden. So the idea that John or his people or the F.B.I. were somehow barred from doing their job is insulting to the U.S. government, which was working on Al Qaeda before John ever showed up. This is all my embassy did for ten months. The fact that not every single thing John O'Neill asked for was appropriate or possible does not mean that we did not support the investigation."
Snip...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.
Snip...When O'Neill told ABC's Isham of his decision to work at the Trade Center, Isham had said jokingly, "At least they're not going to bomb it again." O'Neill had replied, "They'll probably try to finish the job."
Lots of info and names in there. Happy reading.