Since the September 11, 2001, terrorist attacks, reinforced security has included the cockpit – with features that are often redundant.
New information about the Germanwings flight suggest that an unbreakable door, button code locking, and ignored procedures allowed the co-pilot to crash the airplane.
Germanwings owner Lufthansa does not require a cabin crew member to enter the cockpit if one of the pilots steps out.
Cockpit locks are designed to be controlled from the inside, electronically. An outsider can get in if they know the code, but there is an “override” button that can keep them out anyway, if the pilot holds it down.
Some critics say keypad entry could endanger cabin crew if they are pressured to reveal the code.
Below, CNN goes inside an A320 flight simulator to see how someone could be locked out of the cockpit.