[zipper]

I think the least likely is pilot suicide. Theft, flight deck fire, and hijack are all plausible. As well, an “accidental” shoot down by one of the countries within 7 hours of KUL

Okay then, my list at this moment:

1) hijack

2) stolen by crew (one or both)

3) pilot rage ending in suicide or crash

4) sabotage ending in crash

5) catastrophic systems failure (electrical fire, structural failure)

6) remote recall by Boeing for warranty ignition switch replacement

[Tzfat]

Now that you mention it, Boeing is that evil!