Malaysia and or Vietnamese radar not sophisticated enough to record digital data and replay flight path of track and where it intersects below radar coverage to show where FLT370 really went before going below radar?
If one of the Pilots dove Boeing 777 into sea pingers from recorders would give location, but are not pinging?
Someone would still have to pull all the circuit breakers to kill power to the transponder, radios, datalink, telemetry with airline, and know how to pick the correct breakers out of hundreds? Who else but a trained pilot or specialist could accomplish that?
If you stole a Boeing 777 why and where would you land it and what would you do with the passengers? North Korea taking Chinese hostages? Iran taking Chinese hostages? Chinese taking Chinese hostages? Who else was on that flight? SPECTRE or SMERSH or Quantum or Universal Exports or ACME or MMM Enterprises or KGB or CIA or MI6
If the Chinese thought for a moment this was about to be their 9/11 with a jet crashing in say Beijing they would task a sub or other asset and shoot it down. And deny everything.