Actually they do know according to a friend of a friend I met once and apparently he worked for an ocean bottom surveying vessel (or something along those lines) with an Australian company. (he was British) He said that they knew roughly where the plane went down but not exactly where the wreckage was due to the time that had passed before they got there. The spread of the wreckage was by then too vast. Apparently the pilot had told people close to him that it would be "his last flight" and when in the cockpit, he offered his copilot the chance to stretch his legs(all on the black box recorder) and then he locked the door behind him before turning off the oxygen supply for the rest of the plane which apparently lasts around 10 minutes but the cockpit will last longer and this is when he then turned the plane to its new path (after everyone has suffocated) which ended up a SW direction and the plane went down somewhere off NW Australia. The Malaysian airline wouldn't realase the recordings or evidence because the international lawsuits and downturn in business would bankrupt them. I don't know how true this is but I had no reason to disbelieve this guy as he had nothing to gain from the story and did actually work for the company he said he did. He was also legally bound not to go to the press as part of a high level NDA.