@ FDMII
There are other incidents as well, of jets that were at least suspected (if not necessarily confirmed) to have been abruptly wrenched from the sky by "mountain waves" or rotors in the wake of rugged peaks ... but naturally, all of these occurred far below cruise altitude.
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In general, since the first generation of transport jets (when engineers had to discover stuff like the effects metal fatigue on pressurized skins, and the deep-stall vulnerability of rear-engine jets) ...
Airplanes have (very simplistically) two kinds of parts. There are those which can fail, leaving the aircraft with the capacity to land safely; and those whose failure is expected to prevent a safe landing.
In jets after the first generation, catastrophic failure of the components in the second category are really, really rare. They are even more rare at high altitude, with favorable weather.
And even when such must-never-fail components DO break (from causes other than a bomb), usually the jet is able to stay in at least minimally controlled flight for several minutes afterward, or even dozens of minutes -- more than enough time for a Mayday.
I suspect (but don't know, because I haven't plowed through a database of all investigated accidents), that the Metrojet crash would, if not caused by a bomb, be the first one ever to meet the criteria I listed in my earlier post.
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Edited to add: I see you added the Alaska Airlines disaster. Even after the jackscrew mechanism had suffered a severe failure, and the plane pitched into its first steep dive, the flight crew made radio contact with ATC. It's true that they were unable to make a radio call after the jackscrew finally disconnected completely from the HS ... however, the progression of the failure was not so abrupt that the accident occurred without radio communication.
Last edited by Etud_lAvia; 20th Nov 2015 at 17:00.