Reuters is reporting that the stricken Ethiopian airliner that crashed appeared to be trailing smoke and was shuddering before it crashed. This would tend to suggest something other than a software/control failure.

The Ethiopian Airlines plane that crashed killing 157 people was making a strange rattling noise and trailed smoke and debris as it swerved above a field of panicked cows before hitting earth, according to witnesses.

The black boxes have been recovered, so hopefully we might be able to get answers as to what happened.