ALEXANDRIA, Va. – Flight-school instructors recounted Zacarias Moussaoui’s training for a pilot’s license yesterday as the government sought to build its case that he was a credible terrorist threat, not the hopeless malcontent portrayed by his lawyers.

Oklahoma instructor Shohaib Kassam said he flew more than 50 hours with Moussaoui and believed he could have obtained his private pilot’s license with more practice, although he said he was a decidedly below-average student.

And Clarence Prevost, from a Minnesota flight school, said he provided simulator training to Moussaoui on a Boeing 747-400. He said the 747 training is nearly identical to training on the Boeing 757 or 767, the airliners hijacked on September 11, 2001.

Mr. Prevost said Moussaoui had far less training than any other student pilot he had taught, but he assumed Moussaoui was a rich man who was “just fulfilling a dream to play at it.”

Moussaoui had sent an e-mail to the school, which a prosecutor read in court, saying in imperfect English he wanted to “pilot one of these big bird even if I’m not a real professional pilot.”

According to earlier testimony, Moussaoui dreamed in his sleep about piloting a plane and crashing it into the White House, and told his supreme commander, Osama bin Laden, all about it.

That dream has taken on a significant role in Moussaoui’s death-penalty trial. Prosecutors say Moussaoui took flight training to try to make his dream come true. The defense argues those thoughts were the fanciful musings of a deranged mind and maintained he was a disaster as a flight-school student in Oklahoma.

If Moussaoui was capable of attaining his license eventually, he was apparently no standout. Despite his more than 50 hours in the air, was never allowed to fly solo, Mr. Kassam said, even though student pilots can normally do so after 10 to 15 hours of training.

Mr. Kassam said Moussaoui acted normally and occasionally talked about Islam but did not appear to be a radical. Born into the Muslim faith in Pakistan, the instructor said Moussaoui occasionally encouraged him to attend mosque and pray regularly but did not proselytize aggressively.

An Islamic radical testified Wednesday that Moussaoui told him about the dream during a visit Moussaoui made to Malaysia in 2000. The radical, a top official in an Al Qaeda affiliate group called Jemaah Islamiyah, also said during a November 2002 videotape deposition that was played Wednesday that Moussaoui said he had shared his dream with Mr. bin Laden.

Moussaoui does not dispute the dream. When Moussaoui pleaded guilty in April to conspiring with Al Qaeda to hijack aircraft and other crimes, he said bin Laden told him, “Remember your dream.”

But for Moussaoui, the dream is also now a key to his defense. He says that his flight training and efforts to become a pilot have nothing to do with the Sept. 11, 2001, attacks for which he faces a possible death sentence. Instead, he says he was training for a future attack.

Moussaoui’s lawyers argue he was far too unstable for his dreams to ever get off the ground. They elicited testimony Wednesday that top officials in Jemaah Islamiyah considered Moussaoui “cuckoo” and that he was hopeless as a student pilot.

To obtain a death sentence, prosecutors must directly link Moussaoui to the deaths on September 11. They argue that Moussaoui could have prevented the attacks if he had not lied to investigators about his Al Qaeda membership and his plans for a terrorist attack when he was arrested in August 2001 on immigration violations.