The US indictment of Zacarias Moussaoui lists seven conspirators who arrived in the US in advance of the main body of hijackers: Moussaoui, Mohamed Atta, Marwan al- Shehhi, Ziad al-Jarrah, Khalid al-Midhar, Nawaq Alhamzi and Hani Hanjour. These members of this advance party prepared the way for the contingent of hijackers who arrived in America in the Spring of 2001 by, among other things, collecting intelligence about the vulnerabilities of US civil aircraft and airports. They were in a position to collect this intelligence for at least 17 months prior to September 11th, 2001.

D-Day minus 17 months: Establishing the Intelligence Cover

Conspirators in the advance party began applying for admission in flight schools in America in the Spring of 2000. First, Al-Midhar and Alhamzi enrolled in a flight training program in San Diego in April 2000, then, Atta, Al-Shehhi and al-Jarrah enrolled in flight training programs in June 2000 and Moussaoui applied in September 2000 (although his arrival was delayed.) Hanjour, who had been in flight training program 4 year earlier, and so could still claim the credential as a student. briefly joined a flight training program in Arizona in 2001.

None of these flight serving programs would teach the conspirators to fly jet airliners, or even allow them inside one, but they provided them a cover that both would explain their presence in America to immigration and law enforcement authorities and allow them to get technical briefs on aircraft and procedures on the planes they were interested in without attracting suspicion. After all, as pilots-in-training, they had a plausible need to inform themselves about the written and unwritten procedures and problems they might have piloting airliners, and any such questions they asked to trainers, pilots school executives and FAA personnel would simply demonstrate they interest in their chosen profession. They also had a plausible and verifiable excuse for sending away for manuals, computer programs and geo-positioning gear and buying time on expensive simulators for themselves (or others who used their credentials).

Once they established themselves as bona fide aviation students, they remained in these programs for a limited period. Al-Midhar and Alhamzi attended just a few classes— and were airborne in single engine Cessna just twice — before they dropped out. Jarrah also dropped out of his program in Venice, Florida. Moussaoui he left his flight training in Oklahoma after three weeks and never soloed. Hanjour did not need to immediately joined a flight school \since he already had his credential (and when, later, he sought to rent a single-engine plane at Freeway Airport in Bowie, Md., the instructors refused to allow him to solo because they judged his skills too poor to pilot it). Atta and al-Shehhi remained the longest in the flight training program at Huffman Aviation in Florida— nearly six months— but Huffman required only students train for only 8.5 hours a week.

The licenses that they received allowed them to fly only prop planes.

D-Day minus 14 months: Targeting Airliners For Collection

Beginning in early November 2000, the advance party began acquiring technical briefs of Boeing and Airbus airliners. On November 5, 2000, Atta purchased flight deck videos for the Boeing 747 Model 200, Boeing 757 Model 200 from a pilot store in Ohio. These videos would depict the cockpit instrumentation of the airliners. Five weeks later, after he or others had time to study the data, Atta then ordered flight deck videos for the Boeing 767 Model 300ER and the Airbus A320 Model 200 from the same store. Subsequently, to fill in any further gaps, Alhazmi then bought flight deck simulator videos for the Boeing 747 and 777 while Moussaoui bought similar videos for the two other models of the Boeing 747s. In addition, the conspirators acquired flight manuals for these type aircraft.

The videos and manuals, though helpful, would not reveal how the planes would react under extreme conditions, such as, for example, the 180 degree turn while rapidly descending that was later used on the attack on the Pentagon. Nor would their flight school training (which was not on multi-engine jets.) To find out such specific data about the maneuverability of Boeing airliners under real world conditions, they needed access to sophisticated flight simulators. In last week in December, Atta and Al-Shehhi paid $1,500 for three-hour apiece in the Boeing 727 flight simulator at SimCenter Inc. in Opa-locka , Florida. Their status as pilots-in-training was the only credential they needed to test different maneuvers on different routes. (Moussaoui subsequently attempted to book time on a Boeing 747 flight simulator in Minnesota).

Immediately after they completed assembling this data on the performance of Boeings, Atta, al-Shehhi and al-Jarrah departed for unknown destinations in Europe and the Middle east. Here the conspirators involved in the intelligence-collection of the Boeings would be in a position to be debriefed in depth and, if gaps remained, provided with new questions.

D-Day minus 8 ½ months: Unlocking the Cockpits

As early as January 2001, the advance team had begun the final stage of the intelligence operation: reconnoitering actual Boeing Flights. They criss-crossed the country on Boeing 767 and 757, often flying in the first class cabins where they could observe entry into the cockpit. This scouting did not go unnoticed by flight attendants who, after September 11th, reported to the FBI that they recalled men resembling the alleged hijackers photographing the cockpits and taking copious notes. The FBI subsequently estimated from their interviews of flight personnel that their been at least a dozen such observation mission by the conspirators.

One intelligence issue the conspirators had to resolve was how a rapid surprise assault could be made on the cockpits. The FAA requires that all cockpit doors be locked before take- off. But since 1997 the National Transportation Safety Board had held that the FAA should require that each flight\attendant have a cockpit key in his/her possession at all times," or, if airlines consider that the mass distribution of keys is too risky, the cockpit keys must be stored "in a place convenient to the cockpit." It also advised airlines that the flight attendants should have pre-arranged signals, such as a pattern of knocks, to summon the pilots to open the door.

Since the FAA and NTSB requirements and policy on cockpit keys, key boxes and pre- arranged signals and publically disseminated documents, and easily available to pilots-in- training, the conspirators riding in the first-class compartment would have a good idea of what to keep their eyes peeled for aboard these flights. Once they located the key boxes aboard American Airlines 767 and United Airlines 757, or, noted the signals, they had solved the problem of cockpit entry.

Another intelligence issue the conspirators had to resolve was how the assault teams would get weapons and other equipment aboard the planes. In making their reconnaissance flights, they passed though the checkpoints of many different major airports, including Logan and Newark. Here they had the opportunity to test passenger identification, hand baggage scanning, ethnic profiling and other security measures. They could also case the transit lounges for places to cache weapons that other co-conspirators might smuggle past checkpoints so as not to endanger the assault crews. Presumably, bu June when the assault teams were dispatched to the US, they had found security breaches or other means to get the required gear aboard.

D-Day minus 28 days: Unwinding the mission

On August 17, 2001, Moussaoui pilot-in-training legend had failed to convince personnel at a Boeing 747 flight simulator in Minnesota, who reported him to the FBI, and he was taken into custody. By this time, through their liaison work abroad, many of the other conspirators had been compromised in one way or another. Al-Midhar and Alhamzi were photographed meeting suspected terrorists in Malaysia, and their names turned over to the CIA. Al-Jarrah was temporarily detained by police in the United Arab Emirates and Atta was identified by Czech counter-intelligence meeting an officer of Iraqi intelligence in Prague.

They had also left a wide paper trail in getting photo identification for the hijackers, supplying credit cards and establishing residencies for the hijackers cocooned in motel rooms and boarding houses.

By the week of August 24th, the intelligence mission had been completed. Logan airport had been chosen as the airport from which two assault teams would launch the attack on the World Trade. They would seize the cockpits of American Airlines Flight 11 and United Airlines Flight 175, both of which kept sets of cockpit keys in the first-class passenger cabin, and crash them into the two towers of the World Trade Center. Since Logan Airport had no security camera, none of the 10 hijackers on those assault teams could be visually identified. All that would be known about them would be the names under which their tickets were booked. Dulles International Airport had also been selected. An assault team there would seize the cockpit of American Airlines 77 and crash it into the Pentagon. So had Newark Airport. A fourth team there would seize the cockpit United Airlines Flight 93 and crash it into another target in the Washington area. Reservations were made over the Internet, where no ID was needed.
As D-Day approached, the members of the advance team had two options: they could escape by changing their identities or, if they chose suicide, they could die on the planes.