sign of this plane has, has turned up yet, what is the working theory? i don t think there is a working theory. i think of a number of theories. some more possible than others but at the moment we really have no idea where this plane is. this is almost a unique situation. to lose an aircraft of this size with its technology on a normal commercial flight it is extremely unusual. as i say, almost unique and i think it is going to be very challenging finding it. jon: there have been cockpit fires before that have brought down airliners. the swissair crash off newfoundland is one example. certainly possible that the pilot said good night. all of sudden, finds smoke in the cockpit or some kind averaging fire, turns left to try to find a friendly airport and is just over come by smoke and doesn t make it. indeed that is possible and i you have to remember that the 777 is amazing reliable aircraft