Of course it could happen here, you have to admit though the Germanwings pilot was the perfect storm:
-Previous psychiatric problems
-concerns about money and the possible end of the Germanwings brand (so says the girlfriend)
-relationship breakup
-other health problems (reported as eyesight, maybe caused by mental issues)
-fear of loss of licence
-Need to be remembered (according to ex-girlfriend)
I find the most worrying aspect to this whole episode is the fact that there has been clear clues along the way that he was not right. His girlfriend knew, some of his friends admit they new he was seeking help for his depression and it was ongoing. Doctors had told him he was not fit to work and had signed him off, despite all of this though it still fell to just the pilot himself to self report. You can't rely on someone suffering from mental illness to self report.
This is a very tricky issue as the impression some people have at the moment is if you self report something like this then that is career over. Check your loss of licence and income protection, most policies specifically exclude mental illness. It is asking a lot of someone who is ill and possibly doesn't know how bad they are to put their whole livelyhood at risk by self reporting. As we have seen that doesn't always work.