In commercial operations, it is highly desirable that the most direct route between two airports be flown whenever possible. Where that route involves the overflight of extensive areas of high terrain, it is critical that escape routes and procedures be developed and used in the event that an emergency requires that the aircraft must descend to an altitude that is below the Minimum Obstacle Clearance Altitude (MOCA).
General
In many parts of the world, aircraft are routinely flown over terrain that has minimum obstacle clearance altitudes (MOCA) exceeding 10,000'. In most areas, however, the relatively short exposure time to the high terrain negates the requirement for predetermined escape routes and procedures.