the only way to prevent suicidal pilots crashing aircraft is to identify them before hand and stop them from getting onboard.
Everyone agree on that but no-one knows how to do it. In any country that is. The huge discussion/debates and various ideas after Germanwings did not come to anything in the end, because there is no real solution.
Most parents who lost a teenage kid to suicide will tell you they did not see it coming and they lived in the same house. The few that saw their kids was in distress and wanted to help could not prevent it either.. Dealing with mental illnesses is extremely difficult and is a subject very few want to talk about.,