Mode C veil
Encyclopedia
Mode C veil refers to a kind of airspace which surrounds most of primary Class B
Airspace class
The world's navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. Most nations adhere to the classification specified by the International Civil Aviation Organization and described below...

 airports within United States. This airspace extends horizontally to a circle of 30 NM
Nautical mile
The nautical mile is a unit of length that is about one minute of arc of latitude along any meridian, but is approximately one minute of arc of longitude only at the equator...

 radius centered on the airport and extends vertically from the surface up to 10,000 feet MSL. The name refers to the mode of transponder
Transponder (aviation)
A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation...

 operation which is required within this airspace. Out of 37 existing (as of late 2011) Class B airports in the United States, 35 airports (i.e., all but 2) have Mode C veil centered on them. The only two that don't are Houston Hobby Airport and Miramar Naval Air Station.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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