The Times seems to quote officials as saying they know this via ACARS messages. However, assuming the primary radar returns are good enough, this is reasonably

The Times seems to quote officials as saying they know this via ACARS messages. However, assuming the primary radar returns are good enough, this is reasonably inferred by its radar track alone - the chances of hitting 4 separate navigation waypoints (IGARI, VAMPI, GIVAL, IGREX) based on random human flying is pretty much nil. So this may be just confirmation of what most investigators were already assuming. Sad as it is to say, at this point I think the most likely cause is a bizarre pilot suicide. That night one of the pilots likely allowed a dark, dark thought they once had to overtake them for some reason. First this person programmed a set of remote 5-letter nav waypoints into the FMC without the other pilot noticing - not a difficult task by my understanding. Most likely to hide the evidence for insurance reasons, or just out of shame, to hide his actions from the world (a long flight also ensures the CVR will tape over the relevant bits after its 120min loop - CVR/FDR is one of the few things that cannot be disabled from the cockpit of a 777). After the radio handoff, the other pilot left the cockpit for a moment. The perpetrator then set the transponder to standby and disabled ACARS messages from being sent via both VHF and SATCOM. Finally, in order to ensure hypoxia took hold quickly, he set the plane to climb as high as the autopilot would take it (which ended up being ~FL450), and then depressurized the plane, quickly and painlessly killing everyone aboard, including himself. Multiple airline pilots in the airliners.net forums have been discussing these possibilities and they seem to agree that all of these things can be performed by a single pilot, in a few minutes time, entirely from the cockpit. The ghost plane then flew the programmed route until running out of fuel. While this is certainly bizarre, unlikely, and hard to fathom, I posit that it is the least unlikely scenario, because it can be done entirely by one person whose motives we don't understand. Historically, there have been many people who have done bizarre, horrendous things for motives we can't begin to understand - whether due to insanity, sociopathy or zealotry. I truly hope I'm wrong, but I just can't see a grand multinational hijacking conspiracy as being more likely than a sad man wishing to end his sad life in an evil way. If you're thinking of replying to this with your own theory, let me just add that I say all of this not to add flame to the fire of speculation, or to accuse a potentially innocent man of mass murder, but to try and finally put the whole thing to rest in my own mind - I seem to have been rather obsessed with the whole story over the past few days. While the past week has been a flurry of information and misinformation, it's quite likely we will never know what happened to MH370, at least not for a very long time. We need to find the explanations for ourselves that allow us to come to peace with the incident personally, so that we can collectively move on at some point.