The FBI has issued an international alert for a person of interest who took flying lessons at the same U.S. airport in Georgia as two of the 9/11 hijackers. Investigators believe the man -- Zayead Christopher Hajaig -- is now in Britain.
U.S. investigators say Hajaig was exhibiting all the traits of a terrorist.
He is a licensed pilot with a British passport who was in the United States illegally. With no known means of income, he took flight lessons at Gwinnett County Airport-Briscoe Field near Atlanta.
9/11 hijackers Mohamed Atta and Marwan al-Shehhi trained at the same airport.
The FBI says Hajaig was aggressively pressing his flight school to accelerate his training so he could fly larger, more sophisticated planes.
Suspected al Qaeda terrorist Zacarias Moussaoui exhibited similar behavior when he took flight lessons in Eagan, Minn., before the 9/11 attacks.
Considering "what happened in 2001, people are just real wary about what's going on," said Rhett Bartlett, a worker at the airport where Hajaig took lessons.
A government bulletin says Hajaig tried to upgrade his flight rating, even though he was not qualified.
Earlier this year when he learned of the federal investigation, Hajaig abruptly left the country. British police know where he is but have not arrested him.
"We don't know if he's a terrorist or not," said former FBI counterterrorism chief Harry Brandon. "But he's absolutely picture-perfect in a profile, and a profile that would cause intense investigative effort. There's no question about that."
Despite supposedly higher scrutiny of foreign nationals after the 9/11 attacks, Hajaig was able to enroll in flight school in 2002. The government did not require background checks for foreign nationals enrolling in flight schools until October 2004.
Another concern is how Hajaig was able to sneak out of the country after he became the subject of a terrorism investigation.
Law enforcement officials had no comment.
ABC News' Pierre Thomas filed this report for "World News Tonight."