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 million dollars the attacks cost? How could the man who is alleged to have recruited several of the hijack pilots have done this while under investigation of 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, Maine, 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 first-hand, 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.
Here are some of the open questions and what, if anything, is known about their answers.
-- Who provided the nearly half million dollars the attacks cost?
The money was passed from Mohammed to the hijackers by electronic transfer and courier through the United Arab Emirates. Where Mohammed got the money is unknown. He said it came from Osama bin Laden's personal fortune, but investigators have found that the Al Qaeda leader's wealth has been vastly overestimated and that almost all of the organization's estimated $30-million-a-year budget was funded by donations.
Who made the donations to al-Qaida is unknown. Mohammed himself first came to the attention of U.S. investigators for his fund-raising activities in the Persian Gulf, leading some to suspect that he might have raised much of the relatively modest amount of 9/11 money on his own.
-- How could Mohammed Haydar Zammar, a Syrian-born citizen of Germany, have safely recruited the Hamburg pilots when he was under investigation as a possible al-Qaida operative?
Zammar was under surveillance that included having his telephones tapped at the very time he was to have been recruiting the pilots. At one point, U.S. attempts to learn more about Zammar became so disruptive that German officials threatened to throw an American spy out of the country. The Germans nonetheless passed a steady stream of intelligence about Zammar to the Americans. The Islamist scene in Germany was so active throughout the 1990s that, in addition to the Germans and the Americans, intelligence operatives from Syria, Morocco and other Arab governments kept watch on it.
The question about Zammar raises a larger issue on the role of a network of Syrian expatriates across Europe, particularly in Germany and Spain, who had frequent contact with the Hamburg hijackers and with al-Qaida over many years. Many of the Syrians had been members of the Muslim Brotherhood, a group that has had great influence on the evolution of radical Islamist theory in the last half century. Were they witting helpers of the hijackers or, as many of them claim, simply Muslims trying to serve the dictates of their religion by assisting their brothers?
-- Also in Hamburg, what role if any was played by an associate of the hijack pilots named Mohamed Naser Belfas? Belfas, coincidentally or not, on a ttrip to the United States in 2000 applied for and received a Virginia driver's license at the same office and by the same fraudulent means employed by several of the hijackers.
-- What were the relationships, if any, of the hijackers to other al-Qaida cells in the United States?
There is little evidence. There was a network of men in Southern California who assisted two hijackers who lived there, but no links between the men who provided the help and al-Qaida. There are peculiarities, like Atta's trip to Maine, that could be explained by the need to meet contacts, but no known evidence to support such supposition.
The most readily accepted explanation of the Maine trip is that Atta thought he would reduce his exposure to security by going through a smaller airport and Portland was the nearest airport with regular service to Boston. The opposite appears to have happened. Rather than reducing his security exposure, Atta doubled it, passing through security checkpoints in Maine and in Boston.
Different hijackers made numerous trips to Las Vegas. Again, there is no evidence they met other parties there, but no compelling explanation of why they went or what they did there.
-- What was the role, if any, of Zacarias Moussaoui, the Frenchman originally accused in U.S. courts of being the so-called 20th hijacker?
Khalid Shaikh Mohammed said Moussaoui had no intended role in the Sept. 11 attacks. Others still think he might have been a potential pilot replacement. The title of 20th hijacker has subsequently been passed on to a series of men, including Binalshibh, who intended to become a pilot but could not receive a U.S. visa; Zakariya Essabar, a Hamburg associate who also applied unsuccessfully for visas; one of Mohammed's nephews who also was turned down for a visa; and a Saudi man turned away at immigration in Florida.
If Moussaoui was intended to be part of a second wave, what happened to it? Mohammed said he originally intended to plan more attacks, but became too busy. This conveniently eliminated the need to identify who would have carried them out.
-- When did the German pilots first go to Afghanistan? Did bin Laden really choose them for their crucial roles in the attack based on a single meeting when the plot was already in motion in late 1999, as the 9/11 commission report maintains? There are implications that at least some of the Hamburg men traveled to Afghanistan to train in the al-Qaida camps prior to this, but little evidence.
-- Were Binalshibh and hijacker Khalid Almihdhar involved in the bombing of the U.S. destroyer Cole in Yemen? Both were in Yemen when the attack occurred in October 2000.
-- Why do officials of the United Arab Emirates continue to insist that they questioned hijacker Ziad Samir Jarrah at U.S. request in January 2001, when he was en route from Pakistan to Germany immediately after meeting with bin Laden? According to documents obtained by the Los Angeles Times, the Americans have acknowledged to other intelligence services that the UAE informed them of the Jarrah interrogation but said it was a routine check.
UAE officials said the interrogation was hardly routine, that it lasted several hours and Jarrah told them he was about to travel to America to learn to fly. The officials said they passed this information to the United States, but will not say to whom specifically, and that the Americans told them not to hold Jarrah.
-- Why on the morning of 9/11 did the State Department watch list have 61,000 names on it and the Federal Aviation Administration's no-fly list have 12 names? The FAA maintains it could not economically employ a list as large as that maintained by State.
-- One of the most closely examined aspects of the Sept. 11 plot was a meeting of al-Qaida operatives in Kuala Lumpur, Malaysia, in January 2000. American intelligence agencies had advance notice of the meeting and tracked at least two of its participants to Malaysia -- Almihdhar and fellow hijacker Nawaf Alhazmi. Beyond saying they lost track of them afterward, the CIA has not given a satisfying explanation of how agents let them slip away. Neither has there been any explanation of how it came to pass that Almihdhar was met upon arrival at Kuala Lumpur by an Iraqi national employed as a greeter at the airport.
