A question to Lost in Saigon,
Is there (or was there ever) an Emergency Descent Mode available on the 777 AFCS? Some of the more recent systems initiate a 90 degree turn away from the programmed heading followed by a maximum rate descent to around 10,000 feet after a cabin depressurisation is detected.
The similarity of this scenario to the latest version of MA370's possible flight plan - even to matching the SATCOM line of position - bears review.