WASHINGTON — Federal authorities have been aware for years that suspected terrorists with ties to Osama bin Laden were receiving flight training at schools in the United States and abroad, according to interviews and court testimony.

Three days after the attack on the Pentagon and the World Trade Center, FBI Director Robert S. Mueller described reports that several of the hijackers had received flight training in the United States as "news, quite obviously," adding, "If we had understood that to be the case, we would have — perhaps one could have averted this."

However, court documents and interviews with flight-school officials suggest the FBI had warning that potential terrorists were using the schools to obtain flight training. A senior government official acknowledged yesterday that law-enforcement officials were aware of a number of people with links to bin Laden — less than a dozen, the official said — who had attended U.S. flight schools. However, the official said there was no information to indicate the flight students had been planning suicide hijacking attacks.

"We were unable to marry any information from investigations or the intelligence community that talked to their use of this expertise in the events that we saw unfold on the 11th," one government official said.

The involvement of terrorists with flight training includes:

• Two flight-school operators said last week that FBI agents visited them in 1996 to obtain information about several Arab pilots connected to a Pakistani terrorist eventually convicted of plotting to bomb U.S. airliners.

• The flight schools, Coastal Aviation of New Bern, N.C., and Richmor Aviation of Schenectady, N.Y., were two of four that provided flight training to Abdul Hakim Murad in the early 1990s, according to Philippine authorities. Murad was arrested in Manila in 1995 and later convicted in New York of plotting to blow up a dozen U.S. airliners over the Pacific, then crash a suicide plane into CIA headquarters.

• In 1998, FBI agents questioned officials from Airman Flight School in Norman, Okla., about a graduate later identified in court testimony as a pilot for bin Laden, according to Dale Davis, the school's director of operations.

FBI agents returned to Norman two weeks before the Sept. 11 attack, seeking information about another Airman student, Davis said, a French-Moroccan dropout who had entered the country on a visa sponsored by the flight school. The man, Zacarias Moussaoui, had been detained in Eagan, Minn., on an immigration violation after he tried to purchase time on a jet simulator — even though he had never flown solo in a single-engine aircraft.

In addition, court documents from last year's trial of bin Laden associates for the 1998 bombings of American embassies in Kenya and Tanzania contain several references to flight schools and bin Laden pilots.

One government witness, Essam al-Ridi, testified that he had taken classes and taught at the now-defunct Ed Boardman Aviation School in Fort Worth. Al-Ridi also said that in the mid-1990s he purchased a used Saber-40 jet on bin Laden's behalf for $210,000 in Tucson, Ariz. Another witness in the same bombing trial, L'Houssaine Kerchtou, testified that he was sent to a flight school in Nairobi and later served as a pilot for bin Laden.

The issue of how U.S. authorities processed early warning signs that terrorists had infiltrated the flight-school system is certain to be examined in the aftermath of the attack. Suzanne Spaulding, executive director of the National Commission on Terrorism, a congressionally appointed task force, said, "In hindsight, we can see how all these things (flight-school connections) might be relevant and important." But, she said, "it is harder on a day-to-day basis."

Since the attack, the FBI has extended its investigation to dozens of flight schools, including some of the same schools it visited in the years before the attack. According to law-enforcement officials and press reports, the 19 suspected terrorists received flight training from at least 10 U.S. flight schools. At least 44 people sought by the FBI for questioning received some flight instruction.

Dietrich Snell, who helped prosecute Murad, said that although the Pakistani terrorist attended four U.S. flight schools, it would have been difficult for the FBI to connect the schools to the kind of terrorist attack that occurred Sept. 11.