A very interesting read:

The Germanwings tragedy: inside the mind of a pilot (by Michael Bloomfield)

http://www.theguardian.com/commentisfree/2015/mar/27/germanwings-tragedy-pilot-psychiatrist-psychological-evaluation-andreas-lubitz

<< French prosecutors have reported that first officer Andreas Lubitz appeared to want to destroy the aircraft carrying 149 innocent people aboard Germanwings flight 4U9525. As a qualified pilot and a psychiatrist, I have since repeatedly imagined nightmare scenarios in that cockpit. Although we will never know what was truly going through Lubitz's mind as the aircraft plunged, one of the many alarming aspects of this tragedy is that his depression is being quickly blamed. Obviously depression cannot be the sole cause of a likely mass murder. Understanding this could yield many important lessons, and for now, the black box flight recorder will continue to yield vital information. (...) >>

(Michael Bloomfield is a research fellow in psychiatry at Imperial College London)