it sounds as if this prune thread is full of conspiracy theorists.
Let's look at the real possibility of a plane being highjacked in order to carry explosives to a specific target. First of all you would have to highjack it. fair enough, do-able enough. Then you would have to land it on a big enough surface. (potentially difficult, although there are plenty of remote parts of the world). Then you have to be able to refuel it etc and stock it with explosives and so on, while in the meantime the world's military is aware that it's missing and is looking out for it. 239 bodies probably aren't that hard to dispose of - the kinds of people who will highjack a plane and kill themselves and thousands of others in the name of whatever they represent aren't the kind to have much issue with killing a few passengers and crew who are in the way of their plans. but...
Then this plane has to take off from whatever location it's being kept in and fly, unseen, to whatever location is the target. And whatever location that is surely going to be a prominent location and thus said aircraft will need to fly over land in order to get to said location. And people think this is possible without the military seeing it? Not going to happen.
But there's nothing US news loves more than whipping up a bit of muslim hatred....