<As for shooting the plane down, why would they bother to keep that secret under the circumstances? After having suffered 3 attacks that morning, we would've been fully justified in shooting down an airliner under the circumstances, just as those pilots who are flying Combat Air Patrols over the US are prepared to do today if necessary. It's a grim responsibility but one the pilots are prepared to accept.

Good point. How many times have airplanes been "escorted" by fighters since September 11? Everyone on the airliner is well aware that the fighter would shoot them down if the circumstances demanded it. It's no big secret.