Correct me if I am wrong, but the jet supposedly has flown for 8 hours, with a certain amount of time at low altitude yet only had enough fuel to get to Beijing (slightly under 6 hours) and say 45 -60 minutes reserve?
I think aircrafts like the 777 get more than only 45-60 mins reserve fuel for a 6 hour flight.. Logically they would obtain at least haft the trip back if not the whole trip back as reserve (thus 3hrs fuel reserve if not more).
Very interesting read about how ACARS, SATCOM and PING works for a 777 in simple terms, and also explains how investigators figured out the possible flight paths of the missing aircraft.