FANS and ACARS
The earlier message about ACARS messages referred to maintenance messages. Maintenance information is only sent when there is something to report. (Boeing calls this service Aircraft Health Management and messages are sent to the airline AOC and Boeing). With AF447, the equivalent Airbus service sent messages as many aircraft systems were functioning normally for a while during the event.
Was the MH370 aircraft equipped (or enabled) with FANS? Was it using ADS-C? I'm curious why we haven't heard more about FANS messages, which could have transmitted position information as long as the aircraft had power.