The FDR will record that the flight progressed by A/P until fuel exhaustion, and will also record the behaviour of the plane as it made the uncontrolled descent.
Would the recorders be powered with the fuel exhausted? 777 recorders do not run on battery power. Power for the FDR comes from the Right 115Vac Transfer Bus. Power for the CVR comes from Left 115Vac Transfer Bus. DC control for the AC power comes from the main dc busses.
Most likely whoever did this had also thought of pulling the CB-s for the recorders (cf. SilkAir),
You're
assuming the CB-s are accessible from the flight deck... or from other parts of the aircraft without the use of tools.
While not providing any clues to motive, the flaperon can confirm either:
A - the airplane disintegrated in a high energy state, either in the air or hitting the water, suggesting an uncontrolled descent
B - the airplane reached the water in a low energy state that could only have happened through human intervention - ie. someone at the controls.
Or C- kamikaze or poorly controlled human descent
Or D- None of the above.
Activate merry-go-round....