When the cabin crew has finished serving the meal, the flight attendants finally have time to take a break. But what about the pilots? During take-off and initial climb they are fully occupied with flying the aircraft, maintaining contact with air traffic control and monitoring the flight plan. But once the aircraft has reached cruising altitude, a relatively quiet phase beings for the pilots. Aviation authorities stipulate that pilots must take short rest periods on flights lasting more than twelve hours. To enable them to do so, a third pilot, a Senior First officer with a special license, must be on board. He replaces the captain and co-pilot ,afternately. This ensures that the cockpit is always manned by two well-rested pilots, who can then concentrate their altention on the descent and landing.