Actor James Woods tried to report a 9/11 trial run in the month leading up to the attacks on the World Trade Center. Unfortunately, authorities both on the plane and in the airport didn't act on his claims and Woods wasn't contacted again to elaborate until after the attacks took place.
While on a flight from Boston's Logan Airport to Los Angeles, Woods was alone in first class with four other men, all of Middle Eastern descent. Woods noticed that during the six-hour flight, the men did not eat, drink, read or sleep. All four men spent the entire trip sitting upright, only occasionally deviating from position to speak in hushed tones to each other.
Woods mentioned his concerns to a flight attendant, who put him in touch with the first officer of the plane. Nothing more came of that discussion. Once he landed in LA, Woods brought up what he had observed onboard to airport authorities. He was again turned away without immediate investigation.
Obviously Woods' observations alone weren't enough to set off alarms, but post-attack revelations prove he was on to something. Records later revealed that cars used by the hijackers were parked in Logan Airport on September 6, 9 and 10. Woods called the FBI on September 12 to recount what he had experienced. He spoke again with authorities on September 13, though details of his conversations with the FBI have remained private.
In a 2007 interview with Fox News, Woods claims to have gotten confirmation from sources other than the FBI that he was indeed on the same flight as members of the hijacking crew that acted on 9/11.