The really bizarre thing is the changes in direction.
It reached the southern tip of Thailand, before making a sharp turn to the south towards Penang, a highly urbanized and densely populated place (and apparently the hometown of one of the pilots). From there it headed northwest towards the largely uninhabited Andoman Islands, a territory of India. They're saying that India has very good air defence and radar, and that it wouldn't have remained undetected in Indian territory. And if fuel was an issue then why turn back and make the journey longer?
The only thing I can think of is that maybe the hijackers were planning a 9/11 style attack on an urban area, but the pilots or passengers talked them out of it and made off towards a remote place instead. I'm sure I'm overlooking something really obvious though
