Very weird. If it was skyjacked by terrorists, where would they hide a Boeing 777? If their idea was to crash it, kamikaze style, there would be debris found. The whole idea of a terrorist attack is to leave the carnage for all to see, not to hide it.
If the plane was having some kind of mechanical trouble and went down, we would still find debris. If it went into the ocean, we would find jet fuel and oil.
If someone hijacked the plane to divert it to a different location, that would fit the evidence better. Hence the changing course and the transponder being turned off. Also would explain why the plane flew 5 more hours, and why the passenger’s cell phones could receive calls for two days – about the time it takes for a cell phone to run out it’s battery. Maybe the passengers are being held against their will somewhere and the next thing we will hear is a ransom demand.