Source: Daily Mail
Miss Rice revealed that the bunker underneath the White House where she was sheltering with Vice President Dick Cheney began to run out of air.
And she said Mr Bush was forced to resort to an unsecured phone line to talk to Washington because the government communications systems began to fail.
Mr Bush gave the order authorising the airforce to shoot down any commercial airliner that was not responding.
When United 93 came down Ms Rice and other officials believed it may have been shot out of the sky.
Miss Rice added: ‘Everyone in that room thinks that perhaps it’s been shot down.
‘I got on the phone with somebody at the National Military Command centre… just saying “You must know whether or not you’ve shot down a commercial airliner “.
‘That was just a horrible thought that the American air force would have shot down innocent civilians, that was a horrible thought.
