Across the world airspace is structured according to internationally agreed principles.
Airspace is divided into 3-dimensional blocks which are classified from class A to class G airspace.
In the UK class G airspace is uncontrolled. This means there are no restrictions on:
In the UK all other airspace is controlled and aircraft are directed by air traffic controllers. They decide the
safest and most efficient routing for every aircraft (taking into account the surrounding conditions including the
weather and other aviation traffic).
The most efficient routing for any aircraft is one that enables it to reach its destination most directly using the
least amount of fuel. These decisions are sometime referred to as tactical vectoring of aircraft.
Controlled airspace can be split again into other blocks. For example around groups of airports there are terminal
manoeuvring areas and for individual airports radar manoeuvring areas. These are decided on and run by air traffic
control organisations through their operational procedures. Within this airspace air traffic controllers tactically
vector aircraft to get them into and out of airports in the most efficient way.
An international network of routes links these sectors of airspace. Near to airports these are called Standard
Instrument Departure Routes or SIDs and Standard Arrival Routes or STARs. Although aircraft plan to follow these routes
they are not motorways in the sky which aircraft precisely follow but a framework. Aircraft taking off from some
airports are also required to follow specific flight paths called Noise Preferential Routes (NPR) designed to avoid the
overflight of built-up areas where possible (link to page). Once an aircraft reaches the end of the NPR, normally
around 4,000 feet, the air traffic controller determines the path that is flown by an aircraft through the airspace
The basic structure of the UK’s airspace was developed over forty years ago and has changed relatively little since.
Since then there have been huge changes, including radical technological changes in the design of aircraft and the
navigational aids used by pilots and air traffic controllers to direct or route aircraft through the airspace together
with a hundred fold increase in demand for aviation.
Worldwide, work is underway to harmonise, and modernise the way airspace is used. One of the means by which this
will be achieved is referred to as Performance Based Navigation. This is also called area navigation or R-NAV. This
means aircraft changing from navigating by traditional ground based beacons to satellite navigation systems.
Overall this work will allow aviation to make better use of the restricted resources of airspace and runway
capacity. It will also:
To enable this work to happen changes will need to be made to the design and structure of airspace over the UK,
Europe and across the world.
You can read more details on the UK’s work on this, which is known as the Future Airspace Strategy, at www.caa.co.uk/fas. If you're interested or affected by airspace operations, CAP1378 (a civil aviation publication) describes some of the techniques used to manage air traffic in the
UK in more detail.
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