I don't think a tiny Predator drone could have taken down the WTC Tower(s). The structural analysts concluded that it was the massive fuel load that fed the fire that, in turn, created the structural failure. A Predator doesn't carry that kind of fuel load.
My mind is still open on the Shanksville crash. I think that the AF might have had a chance to react (slim) to that particular highjacking. It still doesn't make a difference as to who was responsible -- the Terrorists.
Oh, and I guess that airliner that hit the second tower on live TV was a figment of my imagination. I don't think Steven Spielberg could have faked that one.
No need- they planted demolition charges in both towers in advance ;-)
If the AF did shoot it down I don't think they'd hide the fact. It would be easy to justify and remind wannabes that operations like these hijackings only work once.