the plane when it came down was in the area of no radar contact anyway, but all was fine when it left the Brazilian radar range. For a plane to just 'disappear' it must have had some sort of catastrophic mechanical failure causing it to plummet from the sky, otherwise there would have been more data to go on sent out by the plane's automated systems including the one that reported some sort of electrical fault half an hour or so before it crashed. The plane wouldn't have had a chance of staying intact, as I'm sure you know hitting water from that height is the same as hitting concrete so the chances of anything being remotely intact are slim....and the black box is at the bottom of the sea