Investigators may never know for sure what happened to Air France Flight 447 unless they could find the flight recorders - the so-called black boxes.
To say that will be complicated is an understatement. They might be at the bottom of the ocean - two miles down.
When airliners go down, their black boxes nearly always give the critical clues to what went wrong.
If a black box is injured or can't be retrieved, those secrets go down with it.
In this age of satellite technology, some experts question why airplanes can't beam cockpit conversations and flight data directly to a storage space facility via satellite. Thus create a real time record of the plane's operations.