when the cabin crew has finished serving the meal the flight attenaants 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 motoring the flight plan. but once the air craft has reached cruising altitude, a relatively quite phase begins for the pilots aviation authorities stipulats 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, alternately this ensure that cockpit is always manned by two wen - rested pilots,who can then concentrate their attention on the descent and landing