Joe Biden, the US vice-president, and former presidents George W Bush and Bill Clinton, were among the prominent speakers at a sombre ceremony honouring the passengers and crew of hijacked Flight 93 in Shanksville, Pennsylvania.

They were accompanied by relatives of the 40 victims of the crash.

A white stone wall, bearing the names of those who struggled with the hijackers on the Boeing 757 airliner during the attack, was unveiled in the rural Pennsylvania field where the plane crashed.

Al Jazeera's Kimberly Halkett reports from Shanksville.