The al-Qaida network could be planning a ‘‘Christmas spectacular’’ to hit back at the West after the Taliban’s humiliating defeat, defence experts warned today.

The US plane hijackers murdered stewardesses with knives to draw pilots from their cockpits, it emerged today as investigators began to piece together the full horror of the worst terror attack in history.

Concern that the US could ‘‘over-react’’ to the outrage was voiced by a British terrorism expert.