The general consensus seems to be:
MH370 = unknown
MH17 = accidentally shot down by pro-Russian rebels
Taiwan plane = typhoon/weather
Algerian plane = weather/thunderstorm/lightning strike?
None of them seem to have been caused by a technical fault in the actual plane (i.e. from shoddy maintenance) but were instead caused by forces outside the plane's control.
are you sure about the first one and the technical fault? If it would be kidnapped it would be found somewhere by now. I believe that MH370 was flying too low and shark jumped out of the sea and grabed engine, than plane crashed. Seriously i think it was an technical mistake.