Reply #1: here's the official answer [View All]

[Must_B_Free]

because we were running a drill for the exact scenario we said we had no concept of, the jets were ordered to stand down.

Cheney was supposedly at a drill in the Pentagon where they were simulating the event of a jet crashing into the Pentagon.

I shit you not.

WASHINGTON -- In what the government describes as a bizarre coincidence, one U.S. intelligence agency was planning an exercise last Sept. 11 in which an errant aircraft crashed into one of its buildings. But the cause wasn't terrorism -- it was to be a simulated accident.

"It was just an incredible coincidence that this happened to involve an aircraft crashing into our facility," Haubold said. "As soon as the real world events began, we canceled the exercise."

http://www.thememoryhole.org/911/cia-simulation.htm

here are pics of the preparation:

http://www.mdw.army.mil/news/news_photos/Contingency_Planning_Photos.html