Airspace class (United States)
Encyclopedia
The United States airspace system's classification scheme is to provide maximum pilot flexibility with acceptable levels of risk appropriate to the type of operation and traffic density within that class of airspace - in particular to provide separation and active control in areas of dense or high-speed flight operations.
The Albert ROPER (1919-10-13 The Paris Convention) implementation of International Civil Aviation Organization
(ICAO) airspace class
es defines Classes A through E and Class G. Class F is not used in the United States. The other U.S. implementations are described below. The United States also defines categories of airspace
that may overlap with classes of airspace. Classes of airspace are mutually exclusive. Thus, airspace can be Class E and Restricted at the same time, but it cannot be both Class E and Class B at the same location and at the same time.
Note: All airspace classes except Class G require air traffic control
(ATC) clearance for Instrument flight rules
(IFR) operations.
3-1-1.a) Besides controlled and uncontrolled of airspace, "types" of airspace include Special Use and Other Airspace. (AIM 3-1-1.b)
(18000 feet (5,486.4 m) mean sea level
MSL) to FL600
(approximately 60000 feet (18,288 m) MSL) throughout the United States. (AIM 3-2-2) Unlike the altitude measurements used in other airspace classes, the FLnnn flight levels used in Class A airspace are pressure altitudes referenced to a standardized altimeter setting of 29.92" Hg and thus the true altitudes depend on local atmospheric pressure variations.
Unless otherwise authorized by ATC, all flight operations in Class A airspace must be under ATC control, and must be operating IFR, under a clearance received prior to entry.
Since Class A airspace is normally restricted to instrument flight only, there are no minimum visibility requirements.
Class B airspace is defined around key airport traffic areas, usually airspace surrounding the busiest airports in the U.S.A. according to the number of IFR operations and passengers passing through. The exact shape of the airspace varies from one Class B area to another, but in most cases it has the shape of an inverted wedding cake, with a series of circular “shelves” of airspace of several thousand feet in thickness centered on a specific airport. Each shelf is larger than the one beneath it. Class B airspace normally begins at the surface in the immediate area of the airport, and successive shelves of greater and greater radius begin at higher and higher altitudes at greater distances from the airport. Many Class B airspaces diverge from this model to accommodate traffic patterns or local topological or other features. The upper limit of Class B airspace is normally 10000 feet (3,048 m) MSL. (AIM 3-2-3.a.)
All aircraft entering Class B airspace must obtain ATC clearance prior to entry and must be prepared for denial of clearance. Aircraft must be equipped with a two-way radio for communications with ATC and an operating Mode C transponder
, furthermore aircraft overflying the upper limit of any Class B airspace must have an operating Mode C transponder. Visual Flight Rules (VFR)
flights may proceed under their own navigation after obtaining clearance but must obey any explicit instructions given by ATC. Some Class B airspaces include special transition routes for VFR flight that require communication with ATC but may not require an explicit clearance. Other Class B airspaces include VFR corridors through which VFR flights may pass without clearance (and without technically entering the Class B airspace). (AIM 3-2-3.b.)
VFR flights operating in Class B airspace must have three miles (5 km) of visibility and must remain clear of clouds (no minimum distance). (AIM 3-1-4 and 3-2-3.a.)
Class B airspace has the most stringent rules of all the airspaces in the United States. Class B has strict rules on pilot and student certification. Pilots operating in Class B airspace must have a private pilot's certificate, or have met the requirement of CFR 61.95. These are often interpreted to mean "have an instructor's endorsement for having been properly trained in that specific Class B space." However, it does not apply to student pilots seeking sport or recreational certificates. Some Class B airports (within Class B airspaces) prohibit student pilots from taking off and landing there and are listed in the AIM section 3-2-3(b)2.
In addition to this, some Class B airspaces prohibit Special VFR flights. Certain Class B airports have a Mode C veil
, which is airspace within thirty nautical miles of the airport in which all aircraft must have an operating Mode C transponder (up to 10000 feet (3,048 m) MSL).
and is in effect only during the hours of tower operation at the primary airport. The vertical boundary is usually 4000 feet (1,219.2 m) above the airport
surface. The core surface area has a radius of five nautical miles (9 km), and goes from the surface to the ceiling of the Class C airspace. The upper “shelf” area has a radius of ten nautical miles, and extends from as low as 1200 feet (365.8 m) up to the ceiling of the airspace. (AIM 3-2-4)
All aircraft entering Class C airspace must establish radio communication with ATC prior to entry. The aircraft must be equipped with a two-way radio and an operating Mode C (altitude reporting) radar transponder, furthermore aircraft overflying above the upper limit of Class C airspace must have an operating Mode C transponder. VFR flights in Class C airspace must have three miles (5 km) of visibility, and fly an altitude
at least 500 feet (152.4 m) below, 1000 feet (304.8 m) above, and 2000 feet (609.6 m) laterally from cloud
s. (AIM 3-2-4.c.)
There is no specific pilot certification required. Aircraft
speeds must be below 200 knots (230 mph) at or below 2500 feet (762 m) above the ground, and within 4 nautical miles (7 km) of the Class C airport. (AIM 3-2-4.c.5.)
is generally circular in form and normally extends from the surface to 2500 feet (762 m) above the ground. The outer radius of the airspace is variable, but is generally 5 statute miles. Airspace within the given radius, but in surrounding Class C or Class B airspace, is excluded. Class D airspace reverts to Class E during hours when the tower is closed, or under other special conditions. (AIM 3-2-5)
Two-way communication with ATC must be established before entering Class D airspace, but no transponder
is required. VFR cloud clearance and visibility requirements are the same as Class C. (AIM 3-2-5.b.3)
s). These areas are designated on sectional chart
s. Most airspace in the United States is Class E. The airspace above FL600 is also Class E. (AIM 3-2-6.e.7)
In some areas of the western United States, class E airspace begins at 14500 feet (4,419.6 m) MSL. These areas are usually either very remote or very mountainous (e.g., airspace over many areas of Colorado).
No ATC clearance or radio communication is required for VFR flight in Class E airspace. VFR visibility and cloud clearance requirements are the same as for Class C and Class D airspaces when below 10000 feet (3,048 m) MSL. Above 10000 ft MSL, the visibility requirement is extended to 5 miles (8 km) and the cloud clearance requirement is extended to 1000 feet (304.8 m) below clouds, 1000 feet (304.8 m) above, and 1 miles (1.6 km) laterally. (AIM 3-1-4)
U.S. D.O.T Order JO 7110.65T Effevtice date 02 11 2010:
Class F Airspace "Airspace of defined dimensions within which activites must be confined because of their nature, or within limitations are imposed upon aircraft operations that are NOT a part of those activities, or both. Special use airspace MAY be classified as Class F advisory or Class F restricted."
600. (AIM 3-3-1) There are no entry or clearance requirements for Class G airspace, even for IFR operations. Class G airspace is typically the airspace very near the ground (1200 feet or less), beneath Class E airspace.
Radio communication is not required in Class G airspace, even for IFR operations. Class G is completely uncontrolled.
VFR visibility requirements in Class G airspace are 1 miles (1.6 km) by day, and 3 miles (5 km) by night, for altitudes below 10000 feet (3,048 m) MSL. Beginning at 10,000 feet MSL, 5 miles (8 km) of visibility are required, day and night. Cloud clearance requirements are to maintain an altitude that is 500 feet (152.4 m) below, 1000 feet (304.8 m) above, and 2000 feet (609.6 m) laterally below 10,000 feet MSL; at or above 10,000 feet MSL, they are 1,000 feet below, 1,000 feet above, and 1 mile laterally. By day at 1200 feet (365.8 m) AGL and below, aircraft must remain clear of clouds, and there is no minimum lateral distance.
It should be noted that there are certain exceptions where Class G extends above 1,200 feet AGL. This is usually either over mountainous terrain (e.g., some areas in the Rocky Mountains
), or over very sparsely populated areas (e.g., some parts of Montana
).
clearance, but ATC can advise on the status of the area in some cases (whether or not hazardous activities are in progress, for example). (AIM 3-4-4 and 3-4-6)
. (AIM 3-4-2)
activities are regularly conducted. No special clearance is required to enter MOAs, but pilots should verify with ATC or Flight service station
that no hazardous activity is underway before entering an MOA. (AIM 3-4-5)
They are designated in high volume traffic areas where radar services are available but not otherwise designated as B or C class airspace, such as the Palm Springs Valley in Southern California where high mountainous terrain channels air traffic into the same busy space. TRSA's can sometimes be found around Class D airports as well, such as Chicago Rockford International Airport in Rockford, IL, and Kalamazoo/Battle Creek International Airport in Kalamazoo, MI.
When VFR, pilots need not contact TRACON
prior to entry or while in any TRSA, however it is recommended they do so. There are no specific equipment requirements to operate VFR in a TRSA. If pilots ask for and receive radar services from TRACON, they must comply with heading and altitudes assigned or cancel the service.
and used to provide a safe airspace environment for emergency aircraft operations in situations such as forest fires, disasters, or during Presidential movement. (AIM 3-5-3)
border. Each distinct segment of Class B airspace contains figures indicating the upper and lower altitude limits of that segment in units of one hundred feet, shown as a fraction, e.g., 100 over 40 indicates a ceiling of 10000 feet (3,048 m) MSL and a floor of 4000 feet (1,219.2 m) MSL (SFC indicates that the segment begins at the surface). In some areas each segment may also be assigned a letter for identification during communication with ATC.
In many cases the boundaries of Class B airspace segments are coincident with specific radials from a specific VOR station or with specific distances from such a station; these are normally marked on the chart. In other cases, the boundaries may follow natural topological features or may be defined in other ways, which may or may not be explicitly indicated on the chart.
border. Each distinct segment of Class C airspace contains figures indicating the upper and lower altitude limits of that segment in units of one hundred feet, shown as a fraction, e.g., 100 over 40 indicates a ceiling of 10000 feet (3,048 m) MSL and a floor of 4000 feet (1,219.2 m) MSL. (SFC indicates that the segment begins at the surface, and T indicates that the ceiling ends where overlying Class B airspace begins.)
In many cases the boundaries of Class C airspace segments are coincident with specific radials from a specific VOR station or with specific distances from such a station; these are normally marked on the chart. In other cases, the boundaries may follow natural topological features or may be defined in other ways, which may or may not be explicitly indicated on the chart.
In many cases, the expanse of airspace that is Class E beginning at 1200 feet (365.8 m) AGL is so large that only the areas that differ are marked on the chart. Thus, one may see only external borders within the chart, with the 1200 feet (365.8 m) region extending off the chart.
When Class E airspace begins at altitudes other than 1200 feet (365.8 m) AGL, 700 feet (213.4 m) AGL, or 14500 feet (4,419.6 m) MSL, a delimiting border resembling links in a chain in dark cyan separates the areas, and specific altitudes are marked within them.
The Albert ROPER (1919-10-13 The Paris Convention) implementation of International Civil Aviation Organization
International Civil Aviation Organization
The International Civil Aviation Organization , pronounced , , is a specialized agency of the United Nations. It codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth...
(ICAO) airspace class
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...
es defines Classes A through E and Class G. Class F is not used in the United States. The other U.S. implementations are described below. The United States also defines categories of airspace
Airspace
Airspace means the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere....
that may overlap with classes of airspace. Classes of airspace are mutually exclusive. Thus, airspace can be Class E and Restricted at the same time, but it cannot be both Class E and Class B at the same location and at the same time.
Note: All airspace classes except Class G require air traffic control
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
(ATC) clearance for Instrument flight rules
Instrument flight rules
Instrument flight rules are one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other are visual flight rules ....
(IFR) operations.
Airspace classes
In the U.S. airspace is categorized as regulatory (controlled) - Classes A, B, C, D, and E - and nonregulatory (uncontrolled) - Class G - based on which air traffic control service is provided to IFR flights and some VFR flights. Class F is not used in the U.S. (Aeronautical Information ManualAeronautical Information Manual
In United States aviation, the Aeronautical Information Manual is the Federal Aviation Administration's official guide to basic flight information and ATC procedures....
3-1-1.a) Besides controlled and uncontrolled of airspace, "types" of airspace include Special Use and Other Airspace. (AIM 3-1-1.b)
Class A
Class A airspace extends from FL180Flight level
A Flight Level is a standard nominal altitude of an aircraft, in hundreds of feet. This altitude is calculated from the International standard pressure datum of 1013.25 hPa , the average sea-level pressure, and therefore is not necessarily the same as the aircraft's true altitude either...
(18000 feet (5,486.4 m) mean sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
MSL) to FL600
Flight level
A Flight Level is a standard nominal altitude of an aircraft, in hundreds of feet. This altitude is calculated from the International standard pressure datum of 1013.25 hPa , the average sea-level pressure, and therefore is not necessarily the same as the aircraft's true altitude either...
(approximately 60000 feet (18,288 m) MSL) throughout the United States. (AIM 3-2-2) Unlike the altitude measurements used in other airspace classes, the FLnnn flight levels used in Class A airspace are pressure altitudes referenced to a standardized altimeter setting of 29.92" Hg and thus the true altitudes depend on local atmospheric pressure variations.
Unless otherwise authorized by ATC, all flight operations in Class A airspace must be under ATC control, and must be operating IFR, under a clearance received prior to entry.
Since Class A airspace is normally restricted to instrument flight only, there are no minimum visibility requirements.
Class B
All aircraft entering Class B airspace must obtain ATC clearance prior to entry and must be prepared for denial of clearance. Aircraft must be equipped with a two-way radio for communications with ATC and an operating Mode C transponder
Transponder (aviation)
A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation...
, furthermore aircraft overflying the upper limit of any Class B airspace must have an operating Mode C transponder. Visual Flight Rules (VFR)
Visual flight rules
Visual flight rules are a set of regulations which allow a pilot to operate an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minimums, as specified in the rules of the...
flights may proceed under their own navigation after obtaining clearance but must obey any explicit instructions given by ATC. Some Class B airspaces include special transition routes for VFR flight that require communication with ATC but may not require an explicit clearance. Other Class B airspaces include VFR corridors through which VFR flights may pass without clearance (and without technically entering the Class B airspace). (AIM 3-2-3.b.)
VFR flights operating in Class B airspace must have three miles (5 km) of visibility and must remain clear of clouds (no minimum distance). (AIM 3-1-4 and 3-2-3.a.)
Class B airspace has the most stringent rules of all the airspaces in the United States. Class B has strict rules on pilot and student certification. Pilots operating in Class B airspace must have a private pilot's certificate, or have met the requirement of CFR 61.95. These are often interpreted to mean "have an instructor's endorsement for having been properly trained in that specific Class B space." However, it does not apply to student pilots seeking sport or recreational certificates. Some Class B airports (within Class B airspaces) prohibit student pilots from taking off and landing there and are listed in the AIM section 3-2-3(b)2.
In addition to this, some Class B airspaces prohibit Special VFR flights. Certain Class B airports have a Mode C veil
Mode C veil
Mode C veil refers to a kind of airspace which surrounds most of primary Class B airports within United States. This airspace extends horizontally to a circle of 30 NM radius centered on the airport and extends vertically from the surface up to 10,000 feet MSL. The name refers to the mode of...
, which is airspace within thirty nautical miles of the airport in which all aircraft must have an operating Mode C transponder (up to 10000 feet (3,048 m) MSL).
Class C
Class C space is structured in much the same way as Class B airspace, but on a smaller scale. Class C airspace is defined around airports of moderate importance that have an operational control towerControl tower
A control tower, or more specifically an Air Traffic Control Tower , is the name of the airport building from which the air traffic control unit controls the movement of aircraft on and around the airport. Control towers are also used to control the traffic for other forms of transportation such...
and is in effect only during the hours of tower operation at the primary airport. The vertical boundary is usually 4000 feet (1,219.2 m) above the airport
Airport
An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...
surface. The core surface area has a radius of five nautical miles (9 km), and goes from the surface to the ceiling of the Class C airspace. The upper “shelf” area has a radius of ten nautical miles, and extends from as low as 1200 feet (365.8 m) up to the ceiling of the airspace. (AIM 3-2-4)
All aircraft entering Class C airspace must establish radio communication with ATC prior to entry. The aircraft must be equipped with a two-way radio and an operating Mode C (altitude reporting) radar transponder, furthermore aircraft overflying above the upper limit of Class C airspace must have an operating Mode C transponder. VFR flights in Class C airspace must have three miles (5 km) of visibility, and fly an altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
at least 500 feet (152.4 m) below, 1000 feet (304.8 m) above, and 2000 feet (609.6 m) laterally from cloud
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
s. (AIM 3-2-4.c.)
There is no specific pilot certification required. Aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
speeds must be below 200 knots (230 mph) at or below 2500 feet (762 m) above the ground, and within 4 nautical miles (7 km) of the Class C airport. (AIM 3-2-4.c.5.)
Class D
Class D airspaceAirspace
Airspace means the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere....
is generally circular in form and normally extends from the surface to 2500 feet (762 m) above the ground. The outer radius of the airspace is variable, but is generally 5 statute miles. Airspace within the given radius, but in surrounding Class C or Class B airspace, is excluded. Class D airspace reverts to Class E during hours when the tower is closed, or under other special conditions. (AIM 3-2-5)
Two-way communication with ATC must be established before entering Class D airspace, but no transponder
Transponder
In telecommunication, the term transponder has the following meanings:...
is required. VFR cloud clearance and visibility requirements are the same as Class C. (AIM 3-2-5.b.3)
Class E
Controlled airspace which is neither Class A, B, C nor D. (AIM 3-2-6.a) In most areas of the United States, Class E airspace extends from 1200 feet (365.8 m) AGL up to but not including 18000 feet (5,486.4 m) MSL, the lower limit of Class A airspace. There are areas where Class E airspace begins at either the surface or 700 AGL, these areas are used to transition between the terminal and en-route environments (around non-towered airportNon-towered airport
A non-towered airport, sometimes referred to as an uncontrolled airport, is an airport with no operating tower, or air traffic control unit...
s). These areas are designated on sectional chart
Sectional Chart
In United States aviation, a sectional chart, often called sectional for short, is a type of aeronautical chart designed for navigation under visual flight rules.-Overview:...
s. Most airspace in the United States is Class E. The airspace above FL600 is also Class E. (AIM 3-2-6.e.7)
In some areas of the western United States, class E airspace begins at 14500 feet (4,419.6 m) MSL. These areas are usually either very remote or very mountainous (e.g., airspace over many areas of Colorado).
No ATC clearance or radio communication is required for VFR flight in Class E airspace. VFR visibility and cloud clearance requirements are the same as for Class C and Class D airspaces when below 10000 feet (3,048 m) MSL. Above 10000 ft MSL, the visibility requirement is extended to 5 miles (8 km) and the cloud clearance requirement is extended to 1000 feet (304.8 m) below clouds, 1000 feet (304.8 m) above, and 1 miles (1.6 km) laterally. (AIM 3-1-4)
Class F
Class F is not in use in the United StatesU.S. D.O.T Order JO 7110.65T Effevtice date 02 11 2010:
Class F Airspace "Airspace of defined dimensions within which activites must be confined because of their nature, or within limitations are imposed upon aircraft operations that are NOT a part of those activities, or both. Special use airspace MAY be classified as Class F advisory or Class F restricted."
Class G
Class G airspace includes all airspace not otherwise classified as controlled below flight levelFlight level
A Flight Level is a standard nominal altitude of an aircraft, in hundreds of feet. This altitude is calculated from the International standard pressure datum of 1013.25 hPa , the average sea-level pressure, and therefore is not necessarily the same as the aircraft's true altitude either...
600. (AIM 3-3-1) There are no entry or clearance requirements for Class G airspace, even for IFR operations. Class G airspace is typically the airspace very near the ground (1200 feet or less), beneath Class E airspace.
Radio communication is not required in Class G airspace, even for IFR operations. Class G is completely uncontrolled.
VFR visibility requirements in Class G airspace are 1 miles (1.6 km) by day, and 3 miles (5 km) by night, for altitudes below 10000 feet (3,048 m) MSL. Beginning at 10,000 feet MSL, 5 miles (8 km) of visibility are required, day and night. Cloud clearance requirements are to maintain an altitude that is 500 feet (152.4 m) below, 1000 feet (304.8 m) above, and 2000 feet (609.6 m) laterally below 10,000 feet MSL; at or above 10,000 feet MSL, they are 1,000 feet below, 1,000 feet above, and 1 mile laterally. By day at 1200 feet (365.8 m) AGL and below, aircraft must remain clear of clouds, and there is no minimum lateral distance.
It should be noted that there are certain exceptions where Class G extends above 1,200 feet AGL. This is usually either over mountainous terrain (e.g., some areas in the Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
), or over very sparsely populated areas (e.g., some parts of Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
).
Special use airspace
Some airspace categories have no correlation with ICAO airspace classes but are nevertheless important in United States airspace. The airspace class (A, B, etc.) in which special use airspace is found still controls the requirements and procedures for flying into/through it. (AIM 3-4)Alert and warning areas
Alert and Warning areas contain special hazards that pilots must take into consideration when entering the areas. They do not require a special Air Traffic ControlAir traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
clearance, but ATC can advise on the status of the area in some cases (whether or not hazardous activities are in progress, for example). (AIM 3-4-4 and 3-4-6)
Restricted airspace
Entry into restricted areas is prohibited under certain conditions without a special clearance obtained from the controlling agency obtained directly or via ATC. Examples of restricted areas include test firing ranges and other military areas with special hazards or containing sensitive zones. (AIM 3-4-3)Prohibited airspace
Entry into prohibited areas is forbidden under all circumstances, except for an emergency. Prohibited areas exist over a handful of extremely sensitive locations, such as the White HouseWhite House
The White House is the official residence and principal workplace of the president of the United States. Located at 1600 Pennsylvania Avenue NW in Washington, D.C., the house was designed by Irish-born James Hoban, and built between 1792 and 1800 of white-painted Aquia sandstone in the Neoclassical...
. (AIM 3-4-2)
Military operation area (MOA)
Military operation areas (MOA) are areas in which militaryMilitary
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
activities are regularly conducted. No special clearance is required to enter MOAs, but pilots should verify with ATC or Flight service station
Flight service station
A Flight Service Station is an air traffic facility that provides information and services to aircraft pilots before, during, and after flights, but unlike air traffic control , is not responsible for giving instructions or clearances or providing separation...
that no hazardous activity is underway before entering an MOA. (AIM 3-4-5)
Controlled Firing Areas
Areas in which activities could be hazardous to aircraft and distinguished from other special use airspace in that its activities are suspended immediately when an aircraft might be approaching the area. (AIM 3-4-7)Other Airspace Areas
These areas include: Airport Advisory/Information Services, Military Training Routes, Temporary Flight Restrictions,Parachute Jump Aircraft Operations, Published VFR Routes, Terminal Radar Service Area(TRSA) and National Security Areas. (AIM 3-5)Terminal radar service area (TRSA)
Terminal radar service area, or TRSA, is general controlled airspace wherein ATC provides radar vectoring, sequencing, and separation on a full-time basis for all IFR and participating VFR aircraft. Service provided at a TRSA is called Stage III Service. TRSA's are depicted on VFR aeronautical charts. Pilot participation is urged but is not mandatory. (AIM 3-5-6)They are designated in high volume traffic areas where radar services are available but not otherwise designated as B or C class airspace, such as the Palm Springs Valley in Southern California where high mountainous terrain channels air traffic into the same busy space. TRSA's can sometimes be found around Class D airports as well, such as Chicago Rockford International Airport in Rockford, IL, and Kalamazoo/Battle Creek International Airport in Kalamazoo, MI.
When VFR, pilots need not contact TRACON
Terminal Control Center
A terminal radar approach control is an air traffic control facility usually located within the vicinity of a large airport. Typically, the TRACON controls aircraft within a 20-50 nautical mile radius of the major airport and a number of "satellite airports" between surface and up to between and...
prior to entry or while in any TRSA, however it is recommended they do so. There are no specific equipment requirements to operate VFR in a TRSA. If pilots ask for and receive radar services from TRACON, they must comply with heading and altitudes assigned or cancel the service.
Temporary flight restriction (TFR)
Temporarily restricted airspace is designated by NOTAMNOTAM
NOTAM or NoTAM is the quasi-acronym for a "Notice To Airmen". NOTAMs are created and transmitted by government agencies and airport operators under guidelines specified by Annex 15: Aeronautical Information Services of the Convention on International Civil Aviation...
and used to provide a safe airspace environment for emergency aircraft operations in situations such as forest fires, disasters, or during Presidential movement. (AIM 3-5-3)
VFR chart notation
Specific conventions are used to indicate airspace boundaries on VFR sectional and terminal area charts (TACs) for the United States.Class A
Class A airspace is not shown on VFR charts, but it is assumed to extend from 18000 feet (5,486.4 m) MSL to 60000 feet (18,288 m) MSL everywhere.Class B
Class B airspace is delimited by a heavy cyanCyan
Cyan from , transliterated: kýanos, meaning "dark blue substance") may be used as the name of any of a number of colors in the blue/green range of the spectrum. In reference to the visible spectrum cyan is used to refer to the color obtained by mixing equal amounts of green and blue light or the...
border. Each distinct segment of Class B airspace contains figures indicating the upper and lower altitude limits of that segment in units of one hundred feet, shown as a fraction, e.g., 100 over 40 indicates a ceiling of 10000 feet (3,048 m) MSL and a floor of 4000 feet (1,219.2 m) MSL (SFC indicates that the segment begins at the surface). In some areas each segment may also be assigned a letter for identification during communication with ATC.
In many cases the boundaries of Class B airspace segments are coincident with specific radials from a specific VOR station or with specific distances from such a station; these are normally marked on the chart. In other cases, the boundaries may follow natural topological features or may be defined in other ways, which may or may not be explicitly indicated on the chart.
Class C
Class C airspace is delimited by a heavy magentaMagenta
Magenta is a color evoked by light stronger in blue and red wavelengths than in yellowish-green wavelengths . In light experiments, magenta can be produced by removing the lime-green wavelengths from white light...
border. Each distinct segment of Class C airspace contains figures indicating the upper and lower altitude limits of that segment in units of one hundred feet, shown as a fraction, e.g., 100 over 40 indicates a ceiling of 10000 feet (3,048 m) MSL and a floor of 4000 feet (1,219.2 m) MSL. (SFC indicates that the segment begins at the surface, and T indicates that the ceiling ends where overlying Class B airspace begins.)
In many cases the boundaries of Class C airspace segments are coincident with specific radials from a specific VOR station or with specific distances from such a station; these are normally marked on the chart. In other cases, the boundaries may follow natural topological features or may be defined in other ways, which may or may not be explicitly indicated on the chart.
Class D
Class D airspace is delimited by a thin, dashed cyan line, generally in the form of a circle centered on an airport. A number enclosed in a box surrounded by a similar dashed line (ceiling value) and usually within the Class D area gives the upper limit of the airspace in hundreds of feet (the lower limit of Class D is always the surface). A MINUS ceiling value indicates surface up to but not including that value.Class E
Class E airspace is delimited in different ways depending on its lower altitude limit. Airspace in this class that begins at the default altitude of 14500 feet (4,419.6 m) MSL is not delimited. Class E airspace that begins at 1200 feet (365.8 m) AGL is delimited by a broad, shaded cyan border. Class E airspace that begins at 700 feet (213.4 m) AGL is delimited by a broad, shaded magenta border. Airspace in Class E that begins at the surface is delimited by a thin, dashed magenta line (this type of Class E is most often seen as an extension to Class D airspace that facilitates control of IFR routes to and from an airport).In many cases, the expanse of airspace that is Class E beginning at 1200 feet (365.8 m) AGL is so large that only the areas that differ are marked on the chart. Thus, one may see only external borders within the chart, with the 1200 feet (365.8 m) region extending off the chart.
When Class E airspace begins at altitudes other than 1200 feet (365.8 m) AGL, 700 feet (213.4 m) AGL, or 14500 feet (4,419.6 m) MSL, a delimiting border resembling links in a chain in dark cyan separates the areas, and specific altitudes are marked within them.