Critical area (aeronautics)
(重定向自Critical areas)
In aviation, a critical area refers to a designated area of an airport that all aircraft must remain clear of when one or more ILS systems are in use. The critical area should be avoided when the weather is less than or equal to 2 miles visibility or less than or equal to 800 ft. ceilings. These areas are used to protect against signal interference or attenuation that may lead to navigational errors, or worse.