Airline pilots are frequently falling asleep in the cockpits in flight, particularly on long ocean crossings. Some pilots are spending as much as 10 days away from home, often making flights of 10 hours or more. Their biological clocks are disrupted, making it difficult for them to get proper sleep during layovers. New airplanes are extending flight time because of their longer ranges. Other equipment have made it possible to have two rather than three member crews. The smaller crews are more liable to fall asleep. Computerized navigation equipment and autopilots have lightened pilots workloads, giving them little to do when cruising except monitor instruments. As a result fatigued pilots are more vulnerable to falling asleep. While there has been no evidence that fatigued crews have been responsible for airline crashes there is a great deal of concern.