By Amy Goldstein

The Washington Post

WASHINGTON — The 19 hijackers who carried out the worst act of terror ever to occur on U.S. soil worked with little outside help as a single, integrated group composed of identifiable leaders and shadowy foot soldiers who prepared for their final day in a tight choreography over 18 months.

An examination of public records and dozens of interviews shatters the image of the conspiracy that coalesced immediately following the Sept. 11 attacks.

Based on early, flawed information from federal investigators, initial accounts depicted an operation that was carried out by four compartmentalized cells of terrorists. And because investigations and neighbors were confused by similar or falsified Arabic names, reports emerged that the cells included as many as 10 pilots, who, with wives and children, had blended seamlessly into suburban America.

In fact, it now seems clear that only a single hijacker aboard each of the four commandeered aircraft knew how to fly a plane. Just two of the other hijackers, both linked to terrorist Osama bin Laden, had briefly taken flight lessons.

These six men apparently formed the conspiracy’s leadership. Records and interviews show that this core group, often separated by thousands of miles, remained in the United States the longest and left behind the most visible tracks that, in retrospect, can be seen as highly synchronized preparations.

Some of the leaders were educated, worldly and so intimately connected that three of the four suspected pilots had roomed together in Germany, where they attended the Technical University of Hamburg.

Sophisticated as they were, the leaders were clumsy enough in their English and their manners that they repeatedly provoked notice and annoyance while they were in the United States, if not outright suspicion.

Helping these leaders was a cadre of 13 Saudi Arabian men, most of them younger and less educated, many from their country’s poorest regions. These young Saudis left faint appearances in U.S. public records and seem for the most part to have arrived only in recent months.

Leader or follower, none of the hijackers brought wives or children with them. And contrary to early reports, none of the pilots had worked for Saudi Arabian Airlines.

The FBI investigation into the plot is preliminary, and the conspiracy’s precise nature probably will not be understood for years. Only a fraction of what has been learned about the conspirators by federal investigators is publicly known. Telephone records and airline manifests, for example, would be disclosed only in secret before a grand jury or in a courtroom.

But from the information that is available at the moment, certain patterns already can be gleaned that render a fuller picture of the conspirators.

In particular, an analysis of the hijackers’ visible trails gives greater clarity to the role of Mohamed Atta, the 33-year-old Egyptian lawyer’s son already identified by a government official as the "axle" of the plot. He traveled the most, listed the most addresses, took the most practice flights and had the greatest interaction with other conspirators.

Atta and two of the other suspected pilots — Marwan Al-Shehhi and Ziad Jarrah — belonged to a radical Islamic student group in Hamburg that investigators believe may have been a birthplace of the plot.

More broadly, both the leaders and the followers can be seen to have deployed in pairs. They came together for crucial tasks, such as to get new government identification cards that would ease their passage onto the planes.

The hijackers’ behavior reveals certain incongruities. They were Islamic fundamentalists who nevertheless indulged in Western culture, from fast food to hard liquor. One spent $4,500 on a single airline ticket, yet they haggled over bar tabs, car rental fees and apartment security deposits just days before they were to die.

The most basic incongruity, though, was that the preparations of the 19 hijackers were imperfect.

Some were kicked out of pilot schools. Some had to pay cash for their plane tickets after their credit cards were rejected. Two were late for the Boston flight that was the first to slam into the World Trade Center.

But inexact as it was, their plot succeeded in claiming more than 6,000 lives.

As more of the conspiracy becomes understood, government sources now say that the investigation so far suggests the 19 had no major help in the United States. Sources say that the conspirators were funded with $500,000 from overseas and that the terrorist mission was planned and launched several years ago in Germany, with crucial support in Britain, the United Arab Emirates and Afghanistan.