Security experts have poured scorn on claims from jihadis allied to the Islamic State (IS) group, who are active in the Sinai area, that they downed Flight KGL9268, but examinations of the aircraft wreckage and debris field will enable investigators to definitively pronounce on this theory.
The jet was cruising well above the maximum range of any surface-to-air missile that the jihadists are thought to possess. These are far less powerful than the vehicle-borne Buk system that shot down Malaysia Airlines flight MH17 over Ukraine last year.
Experts have also questioned the logic of why Islamic State's Sinai affiliate would risk inviting a massive international retaliation by such an action when its battle is primarily with the Egyptian state.
BBC security correspondent Frank Gardner says that with Russia fighting a war against IS in Syria, and Egypt's fragile economy in desperate need of tourists, both countries will be hoping this has nothing to do with terrorism.