http://www.nytimes.com/2015/03/26/world/europe/germanwings-airbus-crash.html?_r=0
Among the theories that have been put forward by air safety analysts not involved in the investigation is the possibility that the pilots could have been incapacitated by a sudden event such as a fire or a drop in cabin pressure.
A senior French military official, who spoke on the condition of anonymity because the investigation was continuing, said that the lack of communication from the pilots during the plane’s descent was disturbing, and that the possibility that their silence was deliberate could not be ruled out.
There is a lot of that going on now.