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Airspace Classes and VFR Minimums

If you drive your car across the country, you are likely to encounter a wide range of traffic conditions. Some areas, like those within large cities, will suffer from extreme traffic congestion. Other wide-open areas my have little or no traffic. Many areas will exhibit levels of traffic somewhere in between these extremes.

A similar condition exists in the airspace above the United States. To help controllers and pilots deal with these varying traffic conditions in the sky, United States airspace has been divided into six different classes (A, B, C, D, E, and G). These different classes have different requirements for entry into the airspace, pilot qualifications, radio and transponder equipment, and VFR (Visual Flight Rules) weather minimums.

Class A airspace is the most restricted of these classes. It is the airspace extending from 18,000 feet up to and including 60,000 feet. This high-altitude region is typically used by aircraft traveling at high speeds. Air Traffic Control clearance is required before entry into Class A airspace. Pilots flying in Class A airspace must be instrument rated, and flight in this airspace is always conducted under Instrument Flight Rules (IFR). Two-way radios and an altitude-encoding transponder are required.

Class B airspace is generally found around the nations busiest airports. It is outlined on sectional charts with a thick blue line. Air Traffic Control clearance is required before entry into Class B airspace, and all aircraft entering this airspace must be equipped with two-way radios and an altitude-encoding transponder. VFR weather minimums in Class B airspace require three-mile visibility with operations clear of any clouds.

Class C airspace generally extends around busy airports with operational control towers, radar approach control, and a significant amount of IFR and/or passenger traffic. It is outlined on sectional charts with a solid magenta line. Two-way radio contact with approach control is required before entry into Class C airspace, and all aircraft entering this airspace must be equipped with two-way radios and an altitude-encoding transponder. VFR weather minimums in Class B airspace require three-mile visibility. VFR flights must maintain at least 2000 feet horizontal clearance from clouds, and must remain at least 500 feet below and 1000 feet above any clouds.

Class D airspace generally takes the form of a cylindrical area around airports with operational control towers and levels of traffic less than that found in class B and C. It is outlined on sectional charts with a segmented blue line. A segmented box within this area contains the altitude of the top of the Class D airspace in hundreds of feet. Two-way contact is required before entry into Class D airspace, and all aircraft entering this airspace must be equipped with two-way radios. VFR weather minimums in Class D airspace are the same as for Class C.

Class E airspace is the least restrictive of the controlled airspaces. It is found around some uncontrolled airports, as well as transit routes, and Federal Airways. All airspace between 14,500 feet and 18,000 feet that is not contained in other classes of airspace is also Class E airspace. IFR flights require clearance for entry into Class E areas. VFR flights require no special clearance or equipment. At or below 10,000 feet, the VFR weather minimums are the same as that for Class C and D. Above 10,000 feet, the visibility requirement increases to five statute miles, with one mile horizontal and 1,000 feet vertical separation from any clouds. When Class E airspace extends down to the surface, it is marked with a segmented magenta line. If the lower limit to the airspace is 700 feet above the surface, the airspace is marked with a shaded magenta line. If the airspace extends down to 1,200 feet above the surface, it is marked by a shaded blue line. Other possible altitude boundaries for Class E airspace may be noted numerically along a staggered blue line.

Class G airspace is uncontrolled airspace. By day, one statute mile visibility is required. At 1,200 feet or less above the surface, VFR flights must remain clear of clouds. Above 1,200 feet, VFR flights must maintain 2,000 feet horizontal clearance from clouds, and must remain at least 500 feet below and 1,000 feet above any clouds. Requirements increase for flights at night and flights above 10,000 feet.

In addition to the six standard types of airspace described above, there are areas of Special Use Airspace that have special limitations on flight operations due to activities such as military training, artillery, or missile firing. These areas include Prohibited Areas, Restricted Areas, Alert Areas, Warning Areas, and Military Operations Areas.