Airspace Structure

The ICAO Airspace Classification System

The airspace over the UK and surrounding waters from the surface to FL 245 is divided into two Flight Information Regions (FIR); the London FIR and the Scottish FIR. The airspace above the FIR is known as the Upper Flight Information Region (UIR). The airspace within the FIR/UIR is divided into different types using the ICAO Airspace Classification System.

There are currently six classes of airspace under ICAO Standards and Recommended Practices; these are allocated depending on the need to actively control access to airspace and the nature of the activity that takes place within it. 

  • Classes A, C & D require an air traffic control clearance to enter the airspace and receipt of an air traffic service is mandatory. 
  • Class G is uncontrolled in that any aircraft may use the airspace under The Rules of the Air and although an air traffic service may be available it is not mandated. 
  • Large portions of Class G airspace below 19,500 feet are used extensively by Military and General Aviation.
  • Classes, E and F, are not widely used in the UK and no UK airspace is currently designated as Class B.

The application of each of the airspace classifications and of the services within each of them within the UK FIRs is in accordance with the harmonisation principles of the ECAC Airspace Strategy and any measures that emanate from the European Commission’s Single European Sky policies.

The application of a particular airspace classification to a particular volume of airspace will depend principally upon the number of air traffic movements within it, the complexity of IFR operations within it and also upon the safety hazards posed to public transport flights operating under IFR.

The UK airspace structure needs to evolve and change to meet increasing demand on capacity whilst meeting some key principles:

  • Maintaining the highest standards of safety
  • Reducing the impact to people on the ground
  • Reducing the impact on the environment
  • Accommodating the diverse (sometimes conflicting) requirements of different airspace user groups, to the greatest extent possible.

An overview of each Class of Airspace in the UK:

Class A

  • IFR flights only are permitted

  • All flights are provided with air traffic control service and are separated from each other.

Class C

  • IFR and VFR flights are permitted

  • All flights are provided with air traffic control service 
     
  • IFR flights are separated from other IFR flights and from VFR flights.
     
     
  • VFR flights are separated from IFR flights and receive traffic information in respect of other VFR flights.

Class D

  • IFR and VFR flights are permitted 

  • All flights are provided with air traffic control service

  • IFR flights are separated from other IFR flights and receive traffic information in respect of VFR flights

  • VFR flights receive traffic information in respect of all other flights.

Class E

  • IFR and VFR flights are permitted

  • IFR flights are provided with air traffic control service and are separated from other IFR flights.

  • All flights receive traffic information as far as is practical.

  • Class E shall not be used for control zones.

Class F

  • Uncontrolled.
     

  • IFR and VFR flights are permitted



  • All participating IFR flights receive an air traffic advisory service

  • All flights receive flight information service if requested.

Class G

  • Uncontrolled.
     

  • IFR and VFR flights are permitted and receive flight information service if requested.

For more detailed information regarding the Airspace Classifications view the ENR section of the AIP, with specific reference to:

ENR 1.4 - ATS Airspace Classification

ENR 6.1 - Chart/s of the ATS Airspace Classifications