ASHINGTON, May 14 ó The classified memorandum written by an F.B.I. agent in Phoenix last summer urging bureau headquarters to investigate Middle Eastern men enrolled in American flight schools also cited Osama bin Laden by name and suggested that his followers could use the schools to train for terror operations, government officials said for the first time today.
The memorandum said terrorist groups like Mr. bin Laden's might be sending students to the schools as the first step in what could be a concerted effort to place Islamic militants in the civil aviation industry around the world as pilots, security guards or aircraft-maintenance workers.
The memorandum's existence has been known for months, but few details were available until recent weeks, when some lawmakers and Congressional staff members were allowed to read it. Before today government officials had not revealed that the memorandum included direct references to Mr. bin Laden.
Robert S. Mueller III, who did not become director until two weeks before the attacks, has acknowledged that the bureau gave the memo too little attention. Mr. Mueller has said the bureau lacked adequate analytical capabilities to evaluate it, a failing that he has tried to correct by establishing new analytical units within the F.B.I. and staffing them with new personnel.
One such unit is the Office of Intelligence within the bureau, formed as a direct result of this memorandum. The purpose of the office is assemble and evaluate information related to terrorist threats and to disseminate this information within the bureau or to other federal agencies.
The memorandum was written by an F.B.I. agent in Arizona conducting terrorism investigations of several Middle Eastern men who were attending flight school in the area. People who have read the memorandum said it did not identify anyone by name as a Qaeda follower, did not specify which flight schools should be investigated or explicitly predict the Sept. 11 attacks.
But several lawmakers who have read the Phoenix memorandum described it as the most significant document to emerge in Congressional inquiries into whether the government might have been warned about possible hijackings. Several senators said the letter represented a warning that went unheeded.
The memorandum may not be the only internal document embarrassing to the bureau. In August, an agent speculated in notes, made when investigators sought to explain why Zacarias Moussaoui was enrolled in a Minnesota flight school, that Mr. Moussaoui might be planning to fly a plane into the World Trade Center. Mr. Moussaoui, a French citizen, who was soon arrested on immigration charges, was believed by the United States government to be the intended 20th hijacker on Sept. 11.
F.B.I. officials have said no information available to investigators before Sept. 11 could have prevented the attacks. Even though the Phoenix memorandum referred to Mr. bin Laden's possible use of flight schools, nothing in the letter forecast the Sept. 11 plot. None of the Middle Eastern men who were under investigation in Phoenix had any connection to Al Qaeda or to the Sept. 11 attacks, the officials added.
The bureau explanations have not satisfied some lawmakers. Today, Senator Patrick J. Leahy, Democrat of Vermont and chairman of the Senate Judiciary Committee, wrote to Mr. Mueller, the bureau's director, asking for more information.
Law enforcement officials said today that when the memorandum was received electronically at bureau headquarters in late July, counterterrorism agents reviewed it. But they took no action on its central recommendation, which was to urge the bureau to compile information on the visa applications filled out by foreign students seeking admission to aviation schools.
Several of the Sept. 11 hijackers had studied at flight schools in states like Florida and California. One was Mohamed Atta, who the authorities have concluded was the ringleader of the plot.
Several lawmakers have expressed disbelief that the memorandum failed to set off alarms at F.B.I. headquarters.
Today, however, law enforcement officials said the bureau agents who handled the memorandum were not analysts but investigators who were deeply involved in other high priority cases at the time, including a terror plot uncovered in France and the hunt for a suspect in the October 2000 suicide attack on the Navy destroyer Cole in Yemen. The officials said these agents believed they had little time left to investigate what was regarded at the time as a speculative memorandum from Phoenix.
With hundreds of foreigners in flight schools around the country, officials at bureau headquarters regarded the proposed investigative plan as a "sizable undertaking," one official said. They decided to defer action until they had more time to consider the recommendation.
Instead, bureau officials in Washington referred the memorandum to two field offices. One was the New York office, where Al Qaeda cases had been investigated. But no action was taken before Sept. 11.
In addition, bureau officials have said the Phoenix memorandum had other problems. It was not turned over to an agent in Minneapolis who in August began an investigation of Mr. Moussaoui.
Mr. Moussaoui, who was later charged with conspiring with Mr. bin Laden in the Sept. 11 attacks, represented a puzzling case. Bureau agents believed Mr. Moussaoui might be preparing for a terrorist action but had no evidence that he had broken the law.
Mr. Moussaoui had told the school's instructors that he wanted to train on a flight simulator trip from Heathrow Airport in London to Kennedy Airport in New York.
Based on that information, one agent speculated in an internal meeting last August that Mr. Moussaoui might have intended to crash a plane into the trade center, officials said, confirming a report first published in this week's issue of Newsweek.
Other agents had different theories, involving 747 aircraft, which Mr. Moussaoui wanted to pilot in simulation flights. In a final interview with Mr. Moussaoui, the Minneapolis agent confronted him with the bureau's suspicion that he was preparing for a terrorist operation, but did not ask whether he meant to fly into the trade center towers.
Mr. Moussaoui insisted he had no plans to break the law.