Did al-Qaida trainee warn FBI before 9/11?

"More than a year before 9/11, a Pakistani-British man told the FBI an incredible tale: that he had been trained by bin Laden’s followers to hijack airplanes and was now in America to carry out an attack.  The FBI questioned him for weeks, but then let him go home, and never followed up.  Now, the former al-Qaida insider is talking....
Khan remains surprised that, to this day, the FBI, CIA and Scotland Yard have never asked for his help in identifying the street address of the Lahore safe house where he and dozens of other men were trained.  He says he saw some identifying signs and might be able to locate it today. “I just surprised because [they] never come back to ask some more things," he said. "[The FBI] believed me, but maybe not seriously.” "