Let's back track.
Transponder turned off.
ATC ask aircraft flying ahead to try to make contact on the emergency frequency.
This was achieved. But I have seen no transcript even from memory of what was said. Just that communication was difficult because of static.
But the other Malaysian pilot said he was confident it sounded like the voice of the pilot or co pilot.
Then this avenue of communication stopped as well.
It would be very interesting to know the time line of the erratic flight levels.
Could that call up on the emergency frequency have alerted the innocent pilot to what the other was up to eg switching off the transponder. And a struggle eschewed???
It seems that some sort of conversation happened. If everything was kosher and you were in control of an aircraft and you are contacted on an emergency frequency saying that your transponder is off and ATC have lost you - that would be be more than a casual chat.
And finally what indication if any would appear on the flight deck that the transponder had been turned off. Would there be on screen messages? Alarms.
Specifically would a co-pilot know if a driver in the other seat had disabled these?