This procedure is known as the "Two-Person Rule" (or "Rule of Two"). It was widely implemented by airlines globally following the 2015 Germanwings tragedy to ensure that at no point is a single person left alone in the cockpit. If one pilot needs to leave the flight deck for a physiological break, a member of the cabin crew enters to take their place. The flight attendant does not fly the plane; their role is to monitor the remaining pilot and, more importantly, to operate the door mechanism to let the other pilot back in. This prevents a situation where a lone pilot could intentionally lock the door from the inside and crash the aircraft, or become incapacitated, leaving the cockpit inaccessible to anyone outside the reinforced door.