A magnetic compass aboard an aircraft displays the current magnetic heading of the aircraft, "i.e.," the aircraft's directional orientation relative to the Earth's geomagnetic field, which has a roughly north-south orientation. The compass can be used in turns to verify the aircraft is travelling in the desired direction at the conclusion of a turn. The nature of the instrument and the alignment of the magnetic pole of the earth cause the magnetic compass to have several significant limitations when used for navigation. A pilot aware of those limitations can use the compass effectively for navigation. The compass continues to operate despite failures in the electrical, vacuum or pitot static systems.