Airspace is assigned into categories which determine the level of service provided. In Australia, these range from Class A (typically en route, high level airspace) to Class G (uncontrolled airspace predominantly used by light aircraft). More information on classes of airspace is available.
The service provided by air traffic controllers depends on the class of airspace and there are three broad types:
- separation service—air traffic controllers provide separation services to reduce the risks of collision
- flight information service—provision of advice and information which may be valuable for safe and efficient flight conduct
- traffic information service—information issued to alert the pilot of an aircraft that may be close to his/her position or intended route.
Controlled and uncontrolled airspace
Airspace is categorised as 'controlled' or 'uncontrolled'. Controlled airspace in Australia is actively monitored by air traffic controllers and is divided into a number of different classes and classifications.
To enter controlled airspace, an aircraft must first gain clearance from an air traffic controller. In contrast, no clearance (or supervision by air traffic control) is required to operate in uncontrolled airspace. The large majority of light aircraft and helicopters operate outside or underneath controlled airspace, for example, including aircraft that operate at low levels over Sydney Harbour.
Different areas of controlled airspace are managed by different air traffic controllers.
Terminal airspace
Terminal airspace is the airspace surrounding a major airport, generally within 55-90 kilometres. In the case of some major airports, this airspace extends from ground level up to 18 000 ft (6000 m).
Restricted airspace
In restricted airspace, aircraft movements are restricted in accordance with certain specified permissions. Examples of restricted airspace include airspace around military installations and high density flying operations at an airshow or other large public event. More detail on restricted airspace is available.
No-fly zones
No-fly zones are similar to restricted airspace but are imposed and enforced by the military (usually the Royal Australian Air Force). More information on no-fly zones is available.