It doesn't ring true that the US would plan to hijack a passenger plane like this. Especially not to do it & then play the whole "where's it gone, we know nothing" hoopla.
I can believe that they would want to know whether this sort of thing was technically possible - but why wouldn't they just send up a test plane with no passengers & a US crew who were well in-the-know?
While I do also find the close proximity to OBL's birth date a little spooky - surely, if that had anything to do with this, the plane would have been "reused" to achieve whatever ends on that date? It would have been his 57th birthday too, so not hugely significant I wouldn't have thought?
I am so puzzled by the whole thing though - almost anything could be true. Of course the truth is known, just not by the general public.