• 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, unless they request such a routeing or control 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).

    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). The CAA requires the change sponsor of any permanent change to the published airspace design to follow our airspace change process.

    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.

    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 global standard for navigation performance has now shifted from ground-based navigation aids, such as those we have had in the UK for the last 40 years, to navigation performance based on satellite systems and improved aircraft equipment (‘performance-based navigation’). We anticipate that the number of airspace change proposals will increase as a result of changes to European law; a desire by the International Civil Aviation Organization (ICAO) to move to performance-based navigation; and the goals and objectives of the UK’s Future Airspace Strategy. The Future Airspace Strategy is a collaborative initiative between a range of stakeholders for modernising the UK’s airspace. It sets the overall direction, but does not include details or recommendations about specific airspace designs.