could the pilots have been unaware they were too heavy?
@interflug
The flight was obvoius stable and therefore not stalling when the ACARS messages where sent. But the messages showed that the ADIRU and ISIS lost the airspeed information.
They where 3 houres in the flight. Therfore any overweight (which I highly doubt) at TO would not be an issue given the fuel allready burned.
For me its sounds at this time more like (very)partial panel flying at night likely in clouds, in turbulent air at high altidude with has much lower margins left over.
Thats enough of a recipe to kill even the best pilots around.