A former driver for Osama bin Laden knew the target of the fourth hijacked plane on September 11, a prosecutor has said as he sought to undercut defence arguments that the Guantanamo prisoner was a low-level employee.
Salim Hamdan, the first prisoner to face a US war-crimes trial since World War II, heard bin Laden say the plane was heading for "the dome," an apparent reference to the US Capitol, said Navy Lieutenant Commander Timothy Stone.
The plane crashed in a Pennsylvania field as passengers overcame the hijackers.
"Virtually no one knew the intended target, but the accused knew," Stone told the jury of six US military officers in his opening statement.
Hamdan is charged with conspiracy and aiding terrorism. The defence says the prisoner, a Yemeni with a fourth-grade education, was merely a driver for bin Laden and had no significant role in al-Qaeda's terrorist attacks.
"The evidence is that he worked for wages, he didn't wage attacks on America," Harry Schneider, one of Hamdan's civilian defence lawyers, told the jury. "He had a job because he had to earn a living, not because he had a jihad against America."
But prosecutors say that as bin Laden's personal driver, he helped the al-Qaeda leader evade US retribution after the September 11 attacks and transport weapons for the Taliban in Afghanistan.
To support that claim, prosecutors called as their first witness a US special forces soldier who described finding two surface-to-air missiles in the car Hamdan was driving when Afghan forces captured him in November 2001.
"You will not see evidence from the government that the accused ever fired a shot," Stone said. "But what you will see is testimony regarding the accused's role in al-Qaeda, how he became a member of al-Qaeda and how he helped, facilitated and provided material support for that organisation."
Hamdan faces a maximum life sentence if convicted. The trial is expected to take three to four weeks. The US says it plans to prosecute about 80 prisoners at Guantanamo.