What do you think happened to Malaysia airlines flight ?

i dont know

Either a hijack that went wrong or a very subtle "decompression" which slowly and quietly put the crew and passengers to "sleep". There was no radio communication between ground controllers and the aircraft you would have expected hijackers to have made "demands" or publicised what they were doing, maybe they were carrying out a plan (crash on an Australian City?) and for some reason or other crashed before they could do it or tell the workl why they were doing it. If it was a "decompression"it would have had to be subtle as under normal circumstances the oxygen masks would have automatically dropped down. My original thoughts were that there had been an explosion or a catastrophic explosive decompression both of which would have explained why there was no radio communication, but the fact the aircraft continued for so long on a heading which was completely divorced from it's flight plan throws these two suggestions out.

With the help of terrorists, Pilot could have been kidnapped the flight. Because, He (Zaharia) only capable of stopping communication from the transponder.