The hidden secrets of UK airspace: Airspace classifications

Last month we launched Airspace Explorer, our  free flight tracking and airspace education app. You can download it for free from the app store now and see how our airspace is being used to guide thousands of flights a day.

Our hope is that it will help spread an awareness of the role of airspace as a piece of critical UK infrastructure and an appreciation of the controllers whose job it is to keep everyone flying through it safe.

As such, I’ve been digging into how our airspace is made up, its structures and classifications, and how it remains the foundation of our aviation industry.

Today I’m looking at airspace classifications, the differences between them and what they mean for the people who fly through them. In the UK there are currently five classes of airspace; A,C,D,E and G (we have no Class B airspace in the UK and the last F class airspace was remove of converted in E in 2014).

The classification of the airspace within a FIR determines the flight rules that apply and the minimum air traffic services which are to be provided. Classes A, C, D and E are areas of controlled airspace and G is uncontrolled airspace.

Controlled airspace is provided primarily to protect its users, mostly commercial airliners, and as such aircraft that fly in controlled airspace must be equipped to a certain standard and their pilots must hold certain flying qualifications. Pilots must obtain clearance from Air Traffic Control to enter such airspace and, except in an emergency situation, they must follow ATC instructions implicitly.

Class A

In class A airspace, only Instrument Flight Rules (IFR) flying is permitted. It is the most strictly regulated airspace where pilots must comply with ATC instructions at all times. Aircraft are separated from all other traffic and the users of this airspace are mainly major airlines and business jets.

Class C

Class C airspace in the UK extends from Flight Level (FL) 195 (19,500 feet) to FL 660 (66,000 feet). Both IFR and Visual Flight Rules (VFR) flying is permitted in this airspace but pilots require clearance to enter and must comply with ATC instructions.

Class D

Class D airspace is for IFR and VFR flying.  An ATC clearance is needed and compliance with ATC instructions is mandatory. Control areas around aerodromes are typically class D and a speed limit of 250 knots applies if the aircraft is below FL 100 (10,000 feet).

An important side note regarding aerodromes – an aerodrome is a location from which flight operations take place such as large commercial airports, small General Aviation airfields and Military Air Bases. The term airport may imply a certain stature (having satisfied certain certification criteria or regulatory

requirements) that an aerodrome may not have. So whilst all airports are aerodromes, not all aerodromes are airports.

Class E

Class E airspace is for IFR and VFR use. IFR aircraft require ATC clearance and compliance with ATC instructions is mandatory for separation purposes. VFR traffic does not require clearance to enter class E airspace but must comply with ATC instructions.

Class G

In class G airspace, aircraft may fly when and where they like, subject to a set of simple rules. Although there is no legal requirement to do so, many pilots notify Air Traffic Control of their presence and intentions and pilots take full responsibility for their own safety, although they can ask for help.

Can and often do offer pilots in Class G airspace with a basic flight information service to support their safe flying. An Alerting Service is also provided if necessary to notify appropriate organisations regarding aircraft in need of assistance, Search and Rescue for example.

So that covers airspace classification. I hope it makes sense but feel free to comment if you want to ask a question. Next week I’ll take a look at airspace types. I can sense your excitement!

Don’t forget, you can download Airspace Explorer for iPad right now – and it’s free!