One of them, Mohamed Atta, 33, a trained pilot from the United Arab Emirates, is believed to have met with co-conspirators in Prince George's County before the attack, according to federal investigators in Maryland. He is believed to have helped hijack one of two planes in Boston - American Airlines Flight 11 - and then piloted it south into one of the World Trade Center's twin towers.
The list included six other men who are believed to have been trained as pilots, among them Marwan Al-Shehhi, 23, who lived for a time with Atta in Hollywood, Fla., and in Hamburg, Germany, where both were engineering students. Al-Shehhi was on the second hijacked flight from Boston, United Flight 175, which also smashed into the World Trade Center.
Last night, a man identified as a material witness with information highly relevant to the investigation and considered a high-flight risk was arrested at John F. Kennedy International Airport in New York, said New York City Police Commissioner Bernard Kerik.
In other developments, rescue workers found early yesterday the flight data and voice recorders belonging to Flight 77 at the Pentagon. Searchers uncovered the crucial investigative tool a day after the flight data recorder was found in the western Pennsylvania wreckage. Last night, the voice recorder also was found.
All data recorders were turned over to National Transportation Safety Board investigators. The Pentagon voice recorder was damaged, hampering efforts to recover information from it.
As a group, the hijackers named yesterday were young; most were under 30. They all were believed to be of Middle Eastern descent, but they had most recently lived apparently ordinary lives with their families in places such as Delray Beach, Fla., and Fort Lee, N.J.
FBI Director Robert S. Mueller acknowledged yesterday that part of the great tragedy is knowing that the group capable of such terror was, at least for a time, so close at hand.
"The fact there were a number of individuals who were living here and attending flight school was a surprise," Mueller said. "Obviously, if we understood that to be the case, perhaps one could have averted it."
Investigators continued yesterday to follow thousands of leads that could help re-create the hijackers' final days and weeks and months.
Mueller said FBI agents across the country had served more than 30 search warrants and hundreds of subpoenas. Among items seized were computers and documents that could help trace the movements and plans of the group.
The FBI's activities caused a flurry of attention Thursday evening, when all New York airports were shut down as agents questioned about a dozen people, including the man who was charged last night. Early reports said agents had stopped passengers who had been caught carrying false identification, knives and certificates from a Florida flight school. The FBI denied those reports, saying the passengers were being held for suspected violation of immigration laws.
Early yesterday, investigators said all but one of the persons taken into custody had been released.
The man charged last night was detained after his name turned up on a list of 52 that was contained in a security directive sent by the Federal Aviation Administration to U.S. aircraft operators Thursday, according to officials.
Those named on the list, among them Atta and most of the suspected hijackers, were described as "individuals [who] may be associated with terrorist activities and may travel or attempt to travel by commercial aircraft."
None of those released from detention had connections with the terrorist attacks against the World Trade Center and the Pentagon, said Barry W. Mawn, the assistant FBI director who oversees the New York field office.
Agents working the huge investigation - dubbed "Penttbom" (for Pentagon, twin towers, bomb) - have prepared a list of more than 100 people who were wanted for questioning in connection with Tuesday's events. The list, which was different from the FAA list and has not been made public, was distributed to various federal agencies and about 18,000 police departments and was expected to be continuously revised.
Roughly half of the individuals named on the FAA list had home addresses in Vero Beach, Fla., about a two-hour drive north of Delray Beach, the home address listed for seven of the 19 suspected hijackers.