Updated

The Federal Aviation Administration did not warn airlines to increase security after the arrest last August of student-pilot Zacarias Moussaoui because they believed his confinement ended a threat against aviation, officials said Monday.

FAA spokesman Scott Brenner said the FBI told the agency of Moussaoui's arrest just weeks before the Sept. 11 terrorist attacks.

"Nothing they told us was evidence that there was imminent threat and as a result we issued no bulletins to the airlines or airports," Brenner said. "All we knew was he was in jail. As a result of him being in jail, we did not think a threat was imminent."

Moussaoui, who the FBI says trained at an Al Qaeda affiliated camp in Afghanistan, has been charged as a conspirator in the Sept. 11 terrorist attacks. He was arrested in August while training at a Minnesota flight school, after the FBI became suspicious of his efforts to receive training in flying passenger jets.

News that the FBI told the FAA about Moussaoui's arrest was first reported by the Star Tribune of Minneapolis.

The FAA issued 15 warnings to airlines and airports between January and August 2001 about potential terrorist attacks, but none of the information circulars had any specifics and none ordered specific security improvements.

An April 6, 2001, memo, for example, warned airlines that Middle Eastern terrorists could try to hijack or blow up a U.S. plane. But it cited only "reports that prompt concern about the safety and security of U.S. citizens traveling through the Middle East." The FAA said the potential for a terrorist attack was high, but there were no credible threats against U.S. airlines.

"Nevertheless, some of the currently active groups are known to plan and train for hijackings and have the capability to construct sophisticated (bombs) concealed inside luggage and consumer products," the memo said. "The FAA encourages all U.S. carriers to demonstrate a high degree of alertness."

House aviation subcommittee chairman John Mica, R-Fla., said the FAA acted appropriately because the agency didn't have more to go on.

"Why would they do anything if they didn't have more specific information about any conspiracy?" Mica said. "That's what's lost in all of this, the lack of intelligence. They had a warning in place. They acted with prudence, and can only act, even today, based on specific security threat information."

Kathleen Flynn, who lost her son in the 1988 terrorist bombing of Pan Am 103, said the FAA should have publicized the threats. Just weeks before Pan Am 103 exploded over Lockerbie, Scotland, the U.S. embassy in Helsinki, Finland, received a warning that terrorists would target a Pan Am flight out of Frankfurt, Germany, before Christmas. Flight 103 originated in Frankfurt. The warning was given to U.S. embassies and the airlines, but not to airline passengers.

"You can't pooh-pooh the fact there were hijacking warnings," said Flynn, who served on the White House airline security commission formed after the crash of TWA Flight 800. "It's not up to a couple of bureaucrats in Washington to decide what is credible."