Remember a couple of years ago when that Air France Flight 447 went down in the middle of the Atlantic Ocean? It was on the way from Brazil to Paris. The wreckage has been located on the ocean floor and the black box was recovered, so we are able to find out what went on just before the crash.

The pilot was out of the cockpit on a rest break, and the co-pilot was flying the plane. For some reason the instruments were not accurate - there is speculation that maybe ice was clogging the sensors. So between a less-experienced co-pilot and bad information, they didn't know what the situation was, all they knew was that the plane was in an 'aeronautical stall' meaning the air under the wings wasn't sufficient to support the plane. The solution is to put the nose of the airplane down, but the co-pilot put it up, as I think many of us would have done instinctively (nose down = crash; nose up = soar through the air).

Some accounts I've read say the passengers and flight crew might not have been aware there was a problem before the plane crashed into the ocean - they were in some turbulence when the problems started and took the plane's movements to be caused by it.

Here is a detailed report about the black box data:
Recordings Reveal Final Moments Of Air France 447

As for the passengers, some of them are still strapped in their seats on the ocean floor. Some of the surviving families would like their bodies retrieved, and others say leave them there.