http://www.unansweredquestions.net/timeline/2001/wpost092301.html
FBI Knew Terrorists Were Using Flight Schools
by Steve Fainaru and James V. Grimaldi
The Washington Post
September 23, 2001
http://www.washingtonpost.com/ac2/wp-dyn?pagename=article&node=&contentId=A10840-2001Sep22
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 III 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."
A senior government official yesterday acknowledged law enforcement officials were aware that fewer than a dozen people with links to bin Laden 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.