What happened to Malaysia Airlines Flight 370?

In an age where almost everything is accounted for at all times, it's odd when something as large as an airplane goes missing without a shred of evidence. But that's what happened on March 7 -- a Boeing 777-200 that had 239 people on board vanished. The plane hasn't been found, and investigators reported that it will likely be some time before it is found, because "the ocean is a very big place," according to Wired.