Airspace Classes

The airspace is divided into three dimensional sections, called classes. The purpose of this classification system is to precisely set out which flight rules apply and what interaction is defined between aircraft and ATC (Air Traffic Control). The Airspace Classes are defined by the International Civil Aviation Organization (ICAO) and most countries use this system (although some nations have deviations that are closer to the flight rules that existed before ICAO standardisation). In the following table, you will find an overview of the Classes and their definitions. Note that in some countries, not all classes are actually used (i.e. have not been implemented into legislation).

Class	Flight Rules	Clearance	Aircraft separation
A	IFR or SVFR	ATC Clearance	Separation by ATC
B	IFR, SVFR or VFR	ATC Clearance	Separation by ATC
C	IFR, SVFR or VFR	ATC Clearance	Aircraft operating under IFR and SVFR are separated from each other and from flights operating under VFR. Flights operating under VFR are given traffic information about other VFR flights.
D	IFR, SVFR or VFR	ATC Clearance	Aircraft operating under IFR and SVFR are separated from each other, and are given traffic information about VFR flights. Flights operating under VFR are given traffic information in respect of all other flights.
E	IFR, SVFR or VFR	ATC Clearance only for IFR and SVFR	Aircraft operating under IFR and SVFR are separated from each other. As far as is practical, traffic information is given to all flights about VFR flights.
F	IFR or VFR	No clearances	ATC separation for IFR, as far as practical. Traffic information may be given as about other flights.
G	IFR or VFR	No clearances	No ATC separation. Traffic information may be given as far as practical about other flights.

Classes A to E are referred to as controlled airspace. Classes F and G are uncontrolled airspace. Note that class F is not used in the United States of America, Germany and Australia. Furthermore, every country can, and will, have its own deviations, so when flying you must be familiar with the airspace rules and procedures of the specific country.

VFR weather minimums

When flying under Visual Flights Rules, there are requirements regarding the distance you should keep from clouds and flight visibility minimums. These visual minimum conditions are designed so that pilots are able to avoid collisions with other aircraft by acting on the 'see and avoid' principle. However, to be able to spot an airplane emerging from a cloud and be able to react to it, you must be a minimum distance from it. Note that aircraft separation under VFR conditions is always the responsibility of the VFR pilot!

Class	Flight visibility (miles)	Distance from clouds (miles)
A	Not applicable	Not applicable
B	3	Clear of clouds
C	3	500 feet below, 1000 feet above, 2000 feet horizontal
D	3	500 feet below, 1000 feet above, 2000 feet horizontal
E	3 (less than 10,000 feet msl) 5 (at or above 10,000 feet msl)	500 feet below, 1000 feet above, 2000 feet horizontal 1000 feet below, 1000 feet above, 1 mile horizontal
F
G	1 (Day and below 1200 feet agl) 3 (Night and below 1200 feet agl) 1 (Day and above 1200 feet agl and less the 10,000 feet msl) 3 (Night and above 1200 feet agl and less the 10,000 feet msl) 5 (Above 1200 feet agl and above 10,000 feet msl)	Clear of clouds 500 feet below, 1000 feet above, 2000 feet horizontal 500 feet below, 1000 feet above, 2000 feet horizontal 500 feet below, 1000 feet above, 2000 feet horizontal 1000 feet below, 1000 feet above, 1 mile horizontal

Note : In Class G Airspace, below 1,200 feet above the surface, a helicopter may be operated clear of clouds if flying at a speed that allows the pilot adequate opportunity to see any air traffic or obstruction in time to avoid a collision (FAR).

References

ICAO Annex two (Rules of the Air) and annex 11 (ATC Services). When flying in International airspace the Annex two (Rules of the Air) is the guiding document.

Every country must publish its ATC system, and deviations from the ICAO standards. The two manuals used in the USA are the International Flight Information Manual and the Aeronautical Information Publication.

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