Operation Northern Vigilance, planned months in advance, involves deploying fighter jets to locations in Alaska and northern Canada. Part of this exercise is pure simulation, but part is real world: NORAD is keeping a close eye on the Russians, who have dispatched long-range bombers to their own high north on a similar exercise.

Maj.-Gen. Rick Findley, director of NORAD operations, had just completed the night shift. Usually, Findley would be across town at NORAD headquarters at Peterson Air Force Base. But because of the exercise and the time difference with Russia, he'd been working nights in the mountain. He was just preparing to leave when the disaster began unfolding.

Tom Kimmell FOR THE TORONTO STAR COMMAND CENTRE: Canadian Capt. [Mike Jellinek] was at the helm in Cheyenne Mountain when two hijacked jets hit the World Trade Center and NORAD {ldquo}got really, really busy.{rdquo}