Editing Built-in self-test (section)

===Aviation===

Almost all avionics now incorporate BIST.  In avionics, the purpose is to isolate failing [[line-replaceable unit]]s, which are then removed and repaired elsewhere, usually in depots or at the [[original equipment manufacturer|manufacturer]].  Commercial aircraft only make money when they fly, so they use BIST to minimize the time on the ground needed for repair and to increase the level of safety of the system which contains BIST.  Similar arguments apply to military aircraft.  When BIST is used in flight, a fault causes the system to switch to an alternative mode or equipment that still operates.  Critical flight equipment is normally duplicated, or redundant.  Less critical flight equipment, such as entertainment systems, might have a "limp mode" that provides some functions.