Newly posted audio files depict the horror of 9/11 unfolding in the sky as air traffic controllers struggled to follow the faint tracks of hijacked planes, fighter jets tried in vain to chase them down and a flight attendant made a desperate appeal for help.

Al-Qaida deputy leader Ayman al-Zawahri said the US was being defeated in Afghanistan, Iraq and other fronts in a new video released today, the latest in a series put out by the terror network to mark the anniversary of the September 11 attacks.

The thousands killed on September 11 were being remembered where they died and across America today, the second anniversary of the terrorist attacks.

One of the planes that crashed into the Trade Center was American Airlines