Ok yes, terrorism has brought down planes. The investigation is too earily to rule anything out. The black boxes and debree will lead us to the most likely and most probable cause. But if anyone remembers, the TWA flight long ago, everyone first thought a missle had hit it, turned out it was the plane splitting apart, and the back half of it continuing upwards because of thrust with a trail of flames behind it. The witnesses on the ground had the false perception that it had been hit by a missle. The real cause was a fuel tank explosion that cause the plane to break up.

My bet when all this is done, is that it is more likely that this is mechanical. If it turns out to be terrorists, ok, but that is still the least likely cause of airline disasters.