According to airliners.net, the radar transponder on the plane, picked up by Flight24, has good coverage at that altitude and area of the Med. Sea. If the plane was intact, and descended, it would show up on the radar transponder. The plane just went dead at 37,000 ft. It either broke up in flight (mechanical defect or bomb) or lost all power to the radar transponder.
The pilot didn’t make any distress calls either. It again suggests maybe an instant breakup of the plane for whatever reason.
Egyptian authorities saying plane broke up in air?