If the US Air Force had been notified immediately of the September 11, 2001 hijackings and ordered to intervene, its fighter jets could have shot down all four of the airliners that were used to carry out the attacks, the North American Aerospace Defence Command chief, General Ralph E Eberhart, told a 10-member bipartisan commission probing the incident on Thursday.

Eberhart, who has headed NORAD since February 2000, assured the commission that if the plot were carried out today, the command's planes would be able to shoot down all four planes with time to spare because of improvements implemented since the attacks.

He also warned that NORAD should always be considered a "force of last resort". "Where we really need to focus is destroying these terrorist networks, not allowing them into our country. Don't allow them into our airports. Don't allow them in our aircraft, and if they get in our aircraft, don't let them take control of the airplane", Eberhart said.

After the hearing, Lee H Hamilton, a former Democratic Congressman from Indiana and the panel's vice-chairman, said he was surprised by Eberhart's "extraordinary statement". "He's making a lot of assumptions there about almost instantaneous communications."

Thomas H Kean, the former Republican governor of New Jersey who chairs the commission, said Eberhart "believes that if such an event happened today, they would be capable of taking out all four planes, and I hope he's right".

During the presentation of the last interim report to be issued by the staff of the National Commission on Terrorist Attacks Upon the United States, which is racing to complete a final book-length report by the end of next month, commission staffers played recordings of hijackers' voices in radio transmissions that were picked up by air traffic controllers.