"Paradigm shifts open a window; and, once opened, the window will close. [Fictional al Qaeda terrorist] Ayed observes that 11 September was instantly unrepeatable; indeed, the tactic was obsolete by 10am the same morning. Its efficacy lasted for 71 minutes, from 8.46, when American 11 hit the North Tower, to 9.57, and the start of the rebellion on United 93. On United 93, the passengers were told about the new reality by their mobile phones, and they didn't linger long in the old paradigm - the four-day siege on the equatorial tarmac, the diminishing supplies of food and water, the festering toilets, the conditions and demands, the phased release of the children and the women; then the surrender, or the clambering commandos. No, they knew that they weren't on a commercial aircraft, not any longer; they were on a missile. So they rose up. And at 10.03 United 93 came down on its back at 580mph, in Shanksville, Pennsylvania, 20 minutes from the Capitol," - Martin Amis, in the first of three essay installments in the Observer yesterday.