On December 14, 1999, Algerian Ahmed Ressam tried to enter the U.S. by ferry from Canada. After raising suspicions, “Inspectors examining Ressam’s rental car found the explosives concealed in the spare tire well, but at first they assumed the white powder and viscous liquid were drug-related–until an inspector pried apart and identified one of the four timing devices concealed within black boxes. Ressam was placed under arrest. Investigators guessed his target was Seattle. They did not learn about the Los Angeles airport planning until they reexamined evidence seized in Montreal in 2000; they obtained further details when Ressam began cooperating in May 2001.”
– 9/11 Commission, The 9/11 Commission Report, Pages 178-179