How many times has a jet airline flight suffered a major structural failure not caused by an explosive weapon, which disabled it so suddenly that the flight crew never sent a subsequent radio message?
I haven't yet thought of an example. Anybody?
Well TWA800 comes to mind as well.
But sometimes it was just luck, that the crew was able to communicate or even bring back the crippled plane.
Like for JAL123 or United 811
Also ElAl 1862 could have happened slightly different and lead to an immediate crash
vice versa there are cases where bomb explosions did not immedialtely tore the plane appart, like swiss 330.
I would currently say that in history the number of both occurences is about the same. We have however learned and improved aircraft design, and we do scrap aircraft earlier today due to their high fuel consumption before they become really old, so structural/system failure leading to an immediate loss should be less probably every day.
Still the bomb theory remains a very plausible one, but without hard evidence I will not yet buy it. Most of the wreakage is found, so finding evidence should be possible. Sooner or later.