Self-Criticism and Its Risk
The bureau had been shocked by criticism of its tactics in the investigation of Wen Ho Lee, a nuclear scientist in New Mexico. The bureau was deeply embarrassed by the arrest of Robert P. Hanssen, a senior agent, as a Russian spy. The bureau seemed unable to master the even most basic record-keeping tasks after the agency disclosed that it had failed to turn over thousands of pages of internal documents to the defense team for Timothy J. McVeigh, after he had been convicted of bombing the federal building in Oklahoma City.

Today, Mr. Mueller acknowledged repeatedly that the F.B.I. had failed to perceive warning signs that might have thwarted the hijackings, saying it was an analytical failure that would be fixed by hiring hundreds of new analysts, linguists and information technology experts.

In a sharp departure from past statements that the F.B.I. had no information that might have enabled it to thwart the Sept. 11 hijacking plot, Mr. Mueller said, "I cannot say for sure that there wasn't a possibility we could have come across some lead that would have led us to the hijackers."
http://www.nytimes.com/2002/05/30/national/30ASSE.html