I don’t buy the notion that it was commandeered and landed at a hidden airfield somewhere. That would be far too risky in terms of detection and make their mission very unlikely to succeed. The hijackers would know that the moment authorities realize the plane had been hijacked there would be fighter jets scrambled after them from every nearby air force and satellites searching for them.
Because the clock would be ticking until they were spotted by a nearby country, hijackers taking control of the plane would head directly for their target and try to crash it on their target as soon as possible, in order to minimize the time for air forces to intercept them.
I would guess that the aircraft was hijacked by muzzie terrorists and they began to proceed directly to their intended target in order to crash the plane into it.
Why were they headed in the direction of India? Muzzie terrorists would not crash it into a muslim city like Kuala Lumpur. Their greatest enemies are the US and India.
The flight path suggests they were headed to India. They would love to strike New Delhi or some other Indian city. Their plan may have been to follow the typical flight corridor used by airliners and then veer off and crash it into New Delhi. Other targets might be Bangalore or Hyderabad.
However, it appears that the hijackers did not knew about the aircraft periodically automatically pinging satellites. If they did know about it, then obviously they would have disabled it hours earlier when they shut off the transponder.
Therefore, we can conclude that the plane likely never made it beyond the flying radius from the last ping heard to when the next ping would have been heard. If the pings come every hour, then the plane crashed or landed within an hour of the last ping. This would eliminate possibilities such as flying on to Iran or Pakistan.
Why did they not make it to their target? Perhaps as they were approaching radar distance from India, the terrorists lowered the altitude to just over the water but ended up crashing into the sea, or the passengers realized what was happening and stormed the cockpit.
I read that flying low takes up much more fuel, which would mean they'd crash into the sea wherever they ran out.