The U.S. government has paid $5 million to a man whose concerns led to the arrest of al-Qaida conspirator Zacarias Moussaoui prior to the September 11, 2001, terror attacks.

The U.S. State Department is not identifying the tipster, but media reports say he is 69-year-old Clarence Prevost, a former airline pilot and flight instructor from the state of Minnesota.

Prevost became suspicious after Moussaoui expressed interest in learning how to fly jumbo jets at his flight school, even though he had no experience flying smaller aircraft.

Prevost sought to alert authorities about Moussaoui and later became a key witness at his trial.

The State Department awarded Prevost the $5 million Thursday, as part of its "Rewards for Justice" program, which seeks tips about terrorists and terrorist activities.

Moussaoui pled guilty to six terror conspiracy charges and said he was supposed to be part of a second wave of al-Qaida attacks.

The Moroccan-born French citizen is serving a life sentence without the possibility of parole.

Some information for this report was provided by AP .