So, with 50,000kg on board, you could fly for about 7 hours (and reserves) and go about 2000nm.
This mental exercise seems fairly pointless to me. If you want to hide from the radar, you only need to stay low when you're near ATCs. Presumptive hijackers could stay at 600' for 300nm and that would put them on the other side of Malay peninsula, at which point they could regain altitude and they'd have several million square miles of the Indian Ocean at their disposal. (But they probably wouldn't make it to any "really interesting" places like Afghanistan or Somalia, not without refueling.)