Airspace change process

What is airspace?

In its simplest terms, airspace is the portion of the atmosphere controlled by a State above its territory and areas over the sea within which a State is committed by international treaty to provide air navigation services (which includes air traffic control). It is an invisible national asset. For air traffic control purposes, airspace can be divided into two main categories, controlled and uncontrolled. Controlled airspace is where air traffic control needs to have positive control over aircraft flying in that airspace to maintain safe separation between them. Uncontrolled airspace is airspace where aircraft are able to fly freely without being constrained by instructions in routeing or by air traffic control, although they may request information or a service.

Controlled airspace contains a network of corridors, or airways. They link the busy areas of airspace above major airports. At a lower level, control zones are established around each airport. These portions are therefore nearer the ground and closer to population centres. The CAA has a policy of keeping the volume of controlled airspace to the minimum necessary to meet the needs of UK airspace users and to comply with its international obligations.

The defined blocks of controlled airspace, and flight procedures and routes within them such as standard departure and arrival routes, are together part of the overall airspace design. This airspace design is published in the UK Aeronautical Information Publication (AIP). Overlaying the airspace design are air traffic control operational procedures – written instructions forming a framework within which air traffic controllers make decision as to how to control individual aircraft.

Changes to airspace

Changes to the design of UK airspace are proposed by an airspace change sponsor, usually an airport or a provider of air navigation services (including air traffic control). Guidance on the regulatory process for changing the notified airspace design and planned and permanent redistribution of air traffic, is available in our document CAP1616 Airspace Change.

Airspace change proposals vary greatly in terms of size, scale of impact and complexity. Some may have little noticeable operational or environmental impact. Others may require a complex restructuring of airspace with consequences both for airspace users and the environment, including people on the ground impacted by noise. Because controlled airspace carries with it requirements that affect the aircraft and pilots that fly in it, an airspace change can impact airspace users in different ways. In addition, a revision to air traffic control procedures may not involve a change to the design of UK airspace, but it may still have consequences for other airspace users, the environment and people on the ground. The more impactful of such operational procedure changes are therefore also subject to a CAA approval process.

Subject to operational constraints (including safety), the design of airspace, and the airspace change process, do not specify, or limit future increases in, the volume of air traffic using a piece of airspace at any given point in time. The volume of air traffic using an airport may however be addressed by land-use planning conditions, where relevant.

The number and scale of airspace change proposals which the CAA receives each year varies considerably. Some approaches by sponsors do not go beyond initial outline conversations and never progress to a proposal. Some proposals can last several years between the first conversation and the final decision.

The CAA reformed the airspace change process and introduced CAP1616 Airspace Change in December 2017, to ensure that it meets modern standards for regulatory decision-making, and is fair, transparent, consistent and proportionate. The process ensures that when the CAA decides whether or not to approve a proposal to change UK airspace, it does so in an impartial and evidence-based way that takes proper account of the needs and interests of all affected stakeholders.

The CAP1616 Airspace Change process introduced additional CAA scrutiny and validation of sponsors' work and evidence as they develop proposals; increased requirements relating to transparency and engagement; and introduced new opportunities for those impacted by proposals to have their voices heard.

The airspace change process is designed to align with the Government’s policy on managing airspace. Airspace change options are assessed using WebTAG, a series of guides and spreadsheet tools. The Department for Transport have published guidance explaining what WebTAG is and how it can be used to assess noise impacts.

The legislative framework to airspace change is explained on our website.

Information about the Airspace Modernisation Strategy is available on our website and in document CAP1711.