Malaysia Airlines Flight 370, which has been missing for over three days, appears to have done a u-turn shortly after its transponder stopped transmitting and the plane became officially “missing.”

The plane then reportedly flew for another hour, at least, without its transponder.

CNN, CBS and other news outlets have confirmed the u-turn theory with a senior Malaysian military official.

(UPDATE: You can help find flight 370 via a crowdsourcing site – help to scan sattelite photos for wreckage.)

In the image below, you’ll see that the plane took off from Kuala Lumpur, Malaysia, headed towards Vietnam, the transponder signal then disappeared just before the plane flew over Vietnam, and the plane appears to have done a u-turn, flown back over Malaysia and disappeared somewhere between Malaysia and Indonesia.

The debate now is over whether this absolutely was the Malaysia Air flight – CNN is saying that ground radar spotted a plane, but no one can tell if it was “the” plane because they weren’t receiving information from the Malaysian Air flight’s transponder – why the transponder turned off, and why the plane turned around. Though CNN and others seem to be operating under the assumption that this was Flight 370.

Terrorism is an obvious possibility, but that wouldn’t explain the turn-around, unless the goal was something other than simply blowing the plane up.

While it’s reportedly simple to turn off the plane’s transponder, it’s also possible that some malfunction resulted in the transponder turning off – an electrical failure – and that is why the plane turned around. One expert on CNN said the plane could fly another hour even after a power failure – and that additional hour would put it over the spot in the Sea of Malaca where the latest radar information stops.

If you look at the larger map of the region, it’s not entirely clear where else, other than Indonesia, the plane could have been heading.

Now, one interesting thing to consider is that the plane was headed towards Beijing, China. Assuming it didn’t have a planned stopover, we then know the distance the plane could have flown. Here is the distance the plane could have traveled – though you need to take into account that because the plane turned around it lost a bit of its maximum mileage already:

But there just isn’t a lot in the direction the plane was heading.

In fact, the Boeing 777 has a range of between 5,235 to 9,380 nautical miles, according to Wikipedia. Beijing is 2,700 miles from Kuala Lumpur, so let’s assume that’s the maximum distance – that’s the red circle above – but who knows – we’d need to know how much fuel the plane had, and the weight of the plane, in order to know if it could have traveled three times that distance. The plane is used for flights up to 16 hours long. (FYI – a nautical mile is a bit more than a mile, but it’s close enough for our purposes.)

So the map gets a lot more interesting when you add a few more miles to it, including Iran, Afghanistan, Saudi Arabia, Somalia and more. Of course, they’d have to avoid local radar. Then again, if the plane were picked up by local radar in Indonesia, it wouldn’t have had any identifiying information, so who knows if it was picked up anew anywhere else.

Stay tuned.

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