I don't know abut the A340 but the A320 series has gross weight calculated by the FACs. I generally see a 2 to 4000 pound difference in the "paper" weights the load controllers calculate for flight.
True, but the FACs only make that calculation after take-off, once the aircraft has acquired a state of equilibrium.
The Captain evidently called for rotation at the predetermined (wrong) weight. They should have gone from Flex to Toga at that point, if the jet won't fly off at the normal rotation rate.
True again. This captain stated somewhere that he had flown this aircraft from this airport, many times. I don't expect everyone here to agree with me on this, but with that level of experience, the fact that the take-off was not going according to plan, should have been evident a some point sooner than it actually did become apparent.
I've had an experience in the Airbus where the FAC weight was later found to be considerably greater than the load sheet (Specific Airport where an error in loading process was ultimately discovered)
But, during the take-off, we (Both crew) noticed what appeared as "Lesser" performance than expected at an early stage of the take-off (100 knot call-out) and reacted at that time. Take-off, flight and landing were uneventful. Similarly, this was an airport that we both operated from regularly, and the load sheet weight was "Typical" for that station, although the actual weight was much greater.
I only reflect on this because I'm a bit surprised that a crew with this experience level didn't see it coming sooner.
That said, I completely agree that this could happen to anyone. Thankfully, the only damage was to aircraft and pride.
Just my 2 cents worth....