When materials are getting tired

Fatigue might be the the key of Germanwings accident. Fatigue is still nowadays an endemic structural problem of fuselage and specially of the rear portion of the cabin.

Low cost airlines usually fly short and more than 5 times a day. Each takeoff and landing cycle and the pressurization, ice forming on the wings and depressurization associated with it adds stress and damage to the skin of the plane.

Todd Curtis, a former Boeing safety engineer who is now director of the Airsafe.com Foundation said  to US News "if you see a wing here and three miles later you see a fuselage, one doesn't have to be an expert to speculate that it didn't happen on the ground — that something happened before it impacted".