ping times
If they have ping records covering the start of the flight, would they have a good idea of te turn-around time and its variability from the initial flurry of messages as the flight became established?
Also if they have done some test flights with a MAS B777 which I'm assuming they have done now( if not why not) they can verify position and signal strength and see if it matches the data they have now. Surely they would have done this before sending everyone on these large area searches. Also to prove the initial turn back and military primary radar hits. Lets hope they have.