"Not an exercise"
When you listen to the actual audio tapes of air traffic controllers and others involved during the terrible events of September 11, 2001, the mixture of disbelief and desperation comes across loud and clear.
You can share this experience by visiting the terrific interactive website created by the New York Times, The 9/11 Tapes.
We've been deluged by pictures from that day (and there will be more in the days to come), but the terse words of pilots, flight attendants, and even the hijackers themselves tell another story.
9:01 a.m. "It's escalating, big, big time"
These highly-trained and competent professionals were pulled into a new world where the old realities no longer applied. Nothing had prepared them for responding to a civilian airliner used as a weapon.
The Times website does a great job of giving you an overview of the entire 2 hours, broken up by significant developments. You can both read and listen start to finish, or pick and choose. As you listen, an accompanying map charts the position of the planes.
A great use of interactive media as well as a contribution to our understanding of history on that day.