Flight Radar24 is a compilation of unofficial personal receivers out in the world placed into one website in Russia for us all to watch. Whilst I love the App and use it frequently It doesn't cover all of the planet and is unreliable.
Remember ADS-B transmit receive data is "line of sight" and maybe, just maybe the data you are watching comes to an end because MH 370 moved out of sight of the receiver Flight Radar24 use in that part of the World.
"Not to be used for navigation" or proof of....