Given the sparse but interesting data of pings of the ACARS system but no data, - a
hypothesis to explore is: could this be this is another SwissAir Flight 11 – a fire in the Main Equipment Center (MEC) underneath the cockpit? If there’s a fire a smoke detector illuminates the ‘EQUIP COOLING OVRD’ message on the cockpit EICAS.
see diagram here:
http://www.skybrary.aero/images/B772_MEC_FIRE.jpg
It’s possible after seeing a message the crew began a turnback to Malaysia. But if the fire continued it could knock out communications equipment, which would explain the loss of comms, and blow out the crew oxygen bottle which could cause rapid decompression and crew hypoxia if it went off through the fuselage and/or the fire could have damaged the fly-by-wire flight controls which could explain the continued flight.
While just a hypothesis, unfortunately a 777 had a fire in this exact location – luckily for them on the ground in London Heathrow in Feb 2007. See the UK AAIB report:
http://www.aaib.gov.uk/cms_resources...7%20N786UA.pdf
The report said, “…Prior to this accident the aircraft manufacturer was involved in investigating 11 in-service reports of power panel overheat events, three of which involved major damage to the panels. The affected panels were the P200 and P300, and the affected contactors were the RBTB, Auxiliary Power Breaker (APB)and the Primary External Power Contactor (PEPC).
Now imagine if the fire occurred in the air at 35,000 feet.