It reminds me of Payne Stewart because communications between the pilot and ground seemed normal. Then the plane took a right turn and there was no response from the plane after that. But then, how did the transponders get turned off on MH370? That had to be deliberate or a system failure of some kind. We're just not going to know until we know, and we may never know...
Tho thoughts on that, one from personal experience.
First, commercial aircraft don’t fly at maximum speed but at a lower “cruising” speed in order to both save fuel and leave some ability to speed up if bucking headwinds so they can still arrive on schedule.
In my own experience which doesn’t completely apply in this case on a return flight from New York to Chicago our pilot diverted (with permission I suppose) from his regular flight plan and flew well north of his original flight plan to catch an unusual effect of the jet stream which allowed us to arrive in Chicago almost a half hour earlier than originally scheduled.
How do I know that? The pilot announced to the passengers what he was doing and why before he did it.