To do that, the FBI began working in concert with its many partners to find out everything we could about the hijackers and how they pulled off their attacks. We ran down literally hundreds of thousands of leads and checked every record we could get our hands on, from flight reservations to car rentals to bank accounts.
What emerged from our massive investigation was a sobering portrait of 19 hijackers who carried out their attacks with meticulous planning, extraordinary secrecy, and extensive knowledge of how America works.
The plans were hatched and financed overseas, beginning as long as five years ago. Each of the hijackers came from abroad: fifteen from Saudi Arabia, two from the United Arab Emirates, and one each from Lebanon and Egypt. All 19 entered our country legally, and only three had overstayed the legal limits of their visas on the day of the attacks.
While here, the hijackers did all they could to stay below our radar. They contacted no known terrorist sympathizers. They committed no egregious crimes. They dressed and acted like Americans, shopping and eating at places like Wal-Mart and Pizza Hut, blending into the woodwork all the while. When four got speeding tickets in the days leading up to September 11th, they remained calm and aroused no suspicion. Since none were known terrorists, law enforcement had no reason to question or detain them.
The hijackers also left no paper trail. In our investigation, we have not uncovered a single piece of paper – either here in the U.S. or in the treasure trove of information that has turned up in Afghanistan and elsewhere – that mentioned any aspect of the September 11th plot. The hijackers had no computers, no laptops, no storage media of any kind. They used hundreds of different pay phones and cell phones, often with prepaid calling cards that are extremely difficult to trace. And they made sure that all the money sent to them to fund their attacks was wired in small amounts to avoid detection.
In short, the terrorists had managed to exploit loopholes and vulnerabilities in our systems, to stay out of sight, and to not let anyone know what they were up to beyond a very closed circle.
The investigation was enormously helpful in figuring out who and what to look for as we worked to prevent attacks. It allowed us to see where we as a nation needed to close gaps in our security. And it gave us clear and definitive proof that al Qaeda was behind the strikes.