Immediately after the equipment stopped operating, MH-370 made a series of course changes.
It did a ~160 degree turn (at a very high angle of bank) and flew along the border between Malaysia/Thailand border (probably assuming that military RADAR operators in both countries would assume the flight belonged to the other country). Once passed Malaysia, it then turned north to avoid Indonesia and flew along the Strait of Malacca. [1]
It doesn't show up on RADAR again, but we know it later turned almost directly south after passing the northern tip of Indonesia.
This route comes across as so calculated with the explicit intent of going missing, that it's really hard to justify any scenario that doesn't start with the equipment being turned off intentionally and maliciously.
For me the final proof was that a very very similar route was programmed into the pilot's simulation software at home days before the fatal flight. With that knowledge in hand I consider the cause of the accident pretty clear.
