Modern aircraft are robust machines with high levels of redundancy built in, and rarely fall out of the skies due to a single systems failure.

When they tragically occur, accidents are invariably the result of a complex sequence of events that come together and conspire to doom an airliner, despite the best efforts of those in control to avert a disaster.

Seven days after Air France flight AF 447 disappeared, we know precious little as to what occurred aboard the airliner that night.

We have been told that weather in the region was poor at the time of the crash, but aircraft are designed to withstand all but the most destructive forces that nature can throw at them.

We know that in the few precious minutes before the jet plunged towards the ocean, automated monitoring systems began to transmit a sequence of 24 short error messages.

Although they indicated that critical systems were beginning to shut down, we have no understanding as to what precipitated this flurry of data traffic.

We understand that the auto-pilot was disengaged at the time these error messages were sent.

But we have no clues as to whether this was an un-commanded disengagement prompted by some other systems failure, or whether the pilot took control in a valiant but ultimately failed attempt to rescue his aircraft.

According to the BBC, the mystery is thickening.