Aviation is balance of risk and safety
I came across an article about Flight Deck Security: link here ( Skybrary is really good recourse.) We all remember September 11, 2001 with horror. Thereafter, all aircraft doors were equipped with a flight crew compartment door that is designed to resist penetration by small arms fire and grenade shrapnel, and to resist forcible intrusions by unauthorized persons. Modifications were made to SB or STC. Yes, we have reduced the risk of crew capture. But we have come to the conclusion that one crew member in lock cabin can become a danger like Germanwings Flight 9525 in March 2015 (final report pdf here ). After that, security again had to be revised. Now no one can be left alone in the cockpit. We are constantly faced with new and new problems. It's impossible to foresee everything. In general, it seems to me that all aviation is built on a delicate balance of risk and safety. And people are responsible for the balance. From top management to aircraft cleaner. And ...