NORAD officials have maintained that they would have intercepted and shot down United 93. We are not so sure. We are sure that the nation owes a debt to the passengers of United 93.Their actions saved the lives of countless others, and may have saved either the Capitol or the White House from destruction.

The details of what happened on the morning of September 11 are complex, but they play out a simple theme. NORAD and the FAA were unprepared for the type of attacks launched against the United States on September 11, 2001. They struggled, under difficult circumstances, to improvise a homeland defense against an unprecedented challenge they had never before encountered and had never trained to meet.

At 10:02 that morning, an assistant to the mission crew commander at NORAD’s Northeast Air Defense Sector in Rome, New York, was working with his colleagues on the floor of the command center. In a brief moment of reflection, he was recorded remarking that “This is a new type of war.”

He was, and is, right. But the conflict did not begin on 9/11. It had been publicly declared years earlier, most notably in a declaration faxed early in 1998 to an Arabic-language newspaper in London. Few Americans had noticed it. The fax had been sent from thousands of miles away by the followers of a Saudi exile gathered in one of the most remote and impoverished countries on earth.