Why hasn't anyone claimed it? Simple. Hijacking the plane (or the several hundred passengers) isn't the apex of their plans with it.
My fear is that they use this plane to fly a big dirty bomb over/into a big city. I hope I'm wrong on this, and that the plane is "safely," in the depths of the ocean and the passengers on board are, as JW say, "asleep."
Skeeter
p.s. I read somewheret that Isalam teaches theorcratic lying, just like the JWs. To them, not saying where the plane (or those people are) is to the greater "good".