Actually, this really isn't the case:
1. We are not in chaos. We're shook up, but the streets are calm, people are going about their lives, and life is orderly -- very orderly.
2. I know of very, very few people actually evacuated from NYC, except those directly around Ground Zero. Power has come back on there. Manhattanites are still here. Workers are commuting into Manhattan every day.
3. Communications are fine, except for lines in the buildings that are down.
My son lives a couple of blocks from the Empire State Building. He bailed out after the first tower collapsed and they announced another plane still in the air. It is reasonable to assume, under those circumstances that the terrorists were after the symbolic tall buildings in NYC, and still had some ammunition.