If the plane has flown following most of that 777 trail, then it should at least narrow down a little where it went... but it's very unsure we even find out where it went. If this was planned from the very beginning, it would be well hidden by now.

I wonder what happened to the passengers - and if anyone realized what was happening after several hours.

Sadly, I find it hard to believe that passengers wouldn't have tried to use cellphones, and I'm inclined to think that the cabin became depressurized before the last report of contact (a ping off of an inmarsat sattelite) which is reported as 7.5 hours after takeoff.