Heated pitots getting iced could mean only one thing:
flying straight into the cell,
but at night during lightings, (radar misuse is excluded here),
that can happen only if pilot or pilots in cockpit
were asleep at that half an hour, (prior to coming to the cell).
And if heated pitots iced, why engines would not ?
Consequently gradual electric power loss would come!
"All asleep case" would not be first case.
That’s why FA have to come to "visit" cockpit often during sleeeepy hours.
No parts of aircraft found may suggest pilots ditched the aircraft.
