Hijacker(s) plan a 9/11 type suicide mission into some Asian target. Order pilots to turn off all communication and head to said target. Pilots guess motive and pretend to cooperate, but instead fly/program plane to vast Indian ocean, to spare lives on the ground. By the time hijacker(s) realise they are heading in the wrong direction pilots maybe already killed, but there is not enough fuel to get to any land anyway.