With countless police, intelligence and journalistic examinations and two special congressional inquiries, the Sept. 11 attacks have been among the most investigated criminal acts in history.
The release last week of the final report of the independent 9/11 commission offered the nation a comprehensive overview of the origin and execution of the attacks. What the nation does not have are answers to all the outstanding questions, some of them fundamental:
Who provided the nearly half a million dollars it cost to carry out the attacks? How could the man who is alleged to have recruited several of the hijack pilots have done this while under investigation by at least three intelligence services -- those of the United States, Germany and Morocco? Who, if anyone, assisted the hijackers during their time in the United States?
Some unanswered questions fall more in the category of perplexing curiosities:
Why did Mohamed Atta and another hijacker drive from Boston to Portland, Me., the day before the attacks, then fly back to Boston the next morning, almost missing the flight they intended to hijack?
Still other questions have less to do with the plot itself than the ground from which it sprung:
How did it happen that a single family of Pakistani expatriates in Kuwait, by most accounts an ordinary, pious family devoted to good works, produce five men -- the plot mastermind, Khalid Shaikh Mohammed, and four of his nephews -- who played roles in the attacks?
Many of the open questions might never be resolved. As commission Chairman Thomas H. Kean acknowledged, "There are still some unanswered questions because obviously the people who were at the heart of the plot are dead."
The independent 9/11 commission, formally known as the National Commission on Terrorist Attacks Upon the United States, performed best on the issues it investigated firsthand, which largely were the U.S. government's actions and inactions. Most of its 1,200 interviews dealt with this subject. For information on the plot itself, the commission dealt primarily with reports of investigations by others.
That other reporting by necessity relied on sources of varying credibility. The account of the origin and details of the hijack plot itself come almost entirely from hostile interrogations of two men -- Mohammed and one of his deputies, Ramzi Binalshibh, both of whom are in U.S. custody, but neither of whom has shown much willingness to talk about matters that might implicate others.
