" The FBI issued 216 secret, internal threat warnings between January 1 and September 10, 2001, of which 6 mentioned possible attacks against airports or airlines. The State Department issued 9 separate warnings during the same period to embassies and citizens abroad, including 5 that highlighted a general threat to Americans all over the world. The Federal Aviation Administration issued 15 notices of possible terrorist threats against American airlines.19 "

― Steve Coll , Ghost Wars: The Secret History of the CIA, Afghanistan, and Bin Laden from the Soviet Invasion to September 10, 2001