Captain Sondenheimer of Germanwings Flight 9525 performed multiple attempts to unlock the cockpit door; he tried his code but was it disabled; requested re-entry using the intercom but received no response; finally, tried to physically break down the door but failed, which ended as a crash via suicide by pilot (which has faced several attempts of prevention such as some European, Canadian and Japanese airlines adopted a two-in-cockpit policy as did all Australian airlines for aircraft with fifty or more passenger seats.)
Na
Na
Na
Na
Na
Na