Given the comments I have read regarding security at Sharm, it does seem sensible at this juncture for authorities to investigate the possibility some sort of smuggled device being used to down the airliner.
And given that ISIS urged a holy war against Russia just a couple of weeks ago, 'it does seem sensible at this juncture for authorities to investigate the possibility some sort of smuggled device being used to down the airliner'.
Islamic State urges jihad against Russians, Americans: audio | Reuters
And note that ISIS made this threat against 'crusaders' on Oct 13th - the very day that the Knights Templar were all destroyed by King Philip the Fair. It demonstrates the historical context that they are operating within.