How safe are cockpits? Aviation experts weigh in after security scare on board Horizon Air flight

This most recent incident would probably be pretty hard to prevent: it's kind like if the pilot or co-pilot themselves go nuts. I would think the cockpit should have its own restroom, though. Then they can be sealed in there the whole flight :)

This is completely Preventable. The only people allowed to sit in Jump seats (unused seats in flight deck) are those of active employees in transit, or travelling usually domestically only for pleasure. The employee must have their airline security pass with them at all times in order to do so. If not they must sit in the regular passenger seats. No pass, non-active employees can ever sit there. To completely prevent the incident is to not allow anyone except the pilots operating the flight or when needed the flight Director. Then they are the only persons that you'd have to worry about.