Quick note on 'external' meaning
Listening to BBC Radio four reporting on the statement from the airline that this incident was caused by 'external' sources or actions, I was given the impression that it was intended to mean 'external to the airline', as in, sources beyond their control and not, I'm assuming, related to the maintenance, or a failure, of the airframe itself.
I don't think it necessarily means they think it was caused by an external device, or somesuch meaning, as in a SAM or similar.
I think it meant 'something beyond their control'.
If any Russian speakers wish to comment perhaps on the subtleties of translation?