Flying today involves more than the ABCs
Since September 11, 2001, however, we have seen airspace boundaries grow and shrink; we've seen airspace names change to something different and change back to what they were, and we've seen the flight rules for operation in certain airspace change. These constant modifications are nearly impossible to depict on charts, and it is not always practical to publish them in the regulations. Nonetheless, you are required to know and comply with the rules that apply in the airspace in which you are operating. Now more than ever, preflight planning, including a careful and targeted effort to learn of notams affecting your airspace, should be specifically taught during flight training.
Class A, B, C, D, and E airspace is included under the generic term controlled airspace, which is that "airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification." Class G airspace is defined as uncontrolled airspace.
Class A airspace exists above most of the country, from 18,000 feet msl up to and including flight level 600. Operation in this airspace requires an ATC clearance, two-way radio communications, a transponder/encoder, and unless otherwise authorized, all aircraft must be operated under instrument flight rules.
Class B airspace is generally depicted like an upside-down wedding cake centered over a big airport with a large volume of air traffic. Aircraft must have an ATC clearance before entering Class B airspace, along with two-way radio communications capability and an operating transponder/encoder. This way, air traffic controllers can maintain aircraft separation.
Class C airspace is found around less busy airports that have an operational control tower, a radar approach control, and certain traffic levels. You don't need an ATC clearance to enter the airspace, but you must establish and maintain two-way communications and have an operating transponder/encoder.
Class D airspace surrounds airports with operational control towers without Class B or C airspace, and it is generally depicted as a single cylinder. Two-way radio communications are required; a transponder/encoder is not. When the tower is not in operation, the airspace is reclassified as Class E or G airspace.
Class E airspace is the controlled airspace that is left over. This airspace accommodates both IFR and VFR operations, but VFR flights are not required to have clearances or to communicate with ATC. A transponder/encoder is generally not required, but if you have one, it must be turned on.
Class G airspace is uncontrolled airspace, in which operations may be conducted under IFR and VFR, but no ATC communication is required and no ATC separation is provided. Here is where pilots' see-and-avoid responsibilities serve to keep aircraft separated.
Restricted and prohibited areas are areas of defined dimensions and are usually identified with an area on the surface that is not compatible with overflights. Restricted areas usually involve unusual, often invisible, hazards to aircraft, such as artillery firing, aerial gunnery, or guided missiles. Prohibited areas are established for security or other reasons associated with national welfare, such as preventing overflight of the White House.
A warning area extends three nautical miles from the U.S. coastline and warns pilots of potential danger in that area, and military operations areas identify areas of military training activities. There is no regulation restricting flight in these areas, but pilots are advised to ask ATC if any activities will be taking place in them at the time of a flight, and to avoid flying through that airspace during that time if the answer is yes.
Since September 11, we have seen many notams about temporary flight restrictions (TFRs) and special security instructions in new air defense identification zones (ADIZs). In these cases, the FAA imposed temporary or special restrictions in the interest of national security. The need for these restrictions is not always known in advance and may be subject to constant change.
Proper flight planning is crucial to avoiding flights into TFR and ADIZ airspace. Use all available resources and check them as often as you can.
Kathy Yodice is an attorney with Yodice Associates in Washington, D.C., which provides legal counsel to AOPA and administers AOPA's Legal Services Plan. She is an instrument-rated private pilot.
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