• Airspace modernisation co-sponsor update (July 2020): The Government and the Civil Aviation Authority have asserted our continued commitment to airspace modernisation in a joint statementand we have set out further detail on how we intend to review work on airspace modernisation going forward, including the need to consider how individual organisations may progress airspace changes in these uncertain times.  

    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  Airspace Modernisation Strategy. The AMS replaces the Future Airspace Strategy and sets out the ways, means and ends of modernising airspace through 15 initiatives that will modernise the design, technology and operations of airspace, initially focusing on the period until the end of 2024. The new strategy is in response to the Department for Transport tasking the Civil Aviation Authority with preparing and maintaining a co-ordinated strategy and plan for the use of UK airspace up to 2040, including modernisation.

  • In 2015, we started reviewing our process and after nearly three years of detailed work and two public consultations, on 13 December 2017 we launched our new process. This process is effective from January 2018. Detailed guidance about the airspace change process and how to follow it is available in our document - Airspace Change: guidance on the regulatory process for changing the notified airspace design and planned and permanent redistribution of air traffic, and on providing airspace information (CAP1616). A third edition of this document effective from 1 February 2020 incorporates a new decision-making process for proposed changes to air traffic control operational procedures which cause a planned and permanent redistribution of air traffic. We call this the 'PPR' process for short. This document also includes guidance on the information the aviation industry should publish to help communities understand noise changes.

    The airspace change process is designed to be transparent, comprehensible and proportionate, and is aligned 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.

    Decisions being developed under the new CAP 1616 process and those continuing under the old CAP 725 process can be found on their respective pages. We have also introduced a page specific to PPR proposals.

    The following documents set out how the process works:




    In October 2018 the Government decided to introduce a wholly new category of airspace change, on which it directed the CAA to have a decision-making role.

    This category is for air traffic control operational procedure changes which alter the way the airspace is used within an existing airspace design.

    The Secretary of State amended the Air Navigation Directions 2017 to require the CAA to develop and publish procedures, and guidance on such procedures, for the development, consideration and determination of certain types of these proposals. Consequently, from 1 February 2020, an air navigation service provider must assess whether an intended change to air traffic control operational procedures might lead to a planned and permanent redistribution of air traffic that would require CAA approval, known as a 'relevant PPR' for short.

    The third edition of CAP 1616 introduces the decision-making process for PPR proposals. The process is a shortened version of that used for changes in airspace design. The expectation is that few PPR proposals will be submitted each year relative to the number of proposed changes in airspace design.

    The CAA must provide a report to the Secretary of State annually outlining, for each proposal for a relevant PPR referred to it under these procedures, the specific type of the relevant PPR, the relevant airport, and whether it was approved.

    Why was the new PPR process needed?

    The Government noted that whereas changes to airspace design were subject to the airspace change process and consulted on, air traffic control procedure changes could be implemented without consultation, even where the noise impacts were similar to those of a change in airspace design. In other words, because changes to procedures alone formed part of an existing, unchanged airspace design, they were outside the airspace change process. The new PPR process rectifies this and ensures that the impacts of a change in air traffic control operational procedure are assessed, consulted on where appropriate, and are subject to a CAA decision.

    Where can I view PPR proposals?

     In due course the CAA will modify the airspace change portal to accommodate PPR proposals so that they can be viewed in the same way as proposed changes in airspace design. In the meantime we are publishing any applications on a dedicated webpage.

    What types of change are in scope of the PPR process?

    This is explained in CAP 1616. To be in scope (known as a 'relevant PPR') the proposal must

    • fall within scope of one or more of Types 1, 2 or 3
    • 1 Lateral shift in flight track of more than a specified distance
    • 2 Redistribution between Standard Instrument Departure routes
    • 3 Change to Instrument Landing System joining point (on approach)


    • relate to an airport which has a Category C or D (or both) approach landing procedure, and/or established Standard Instrument Departure routes published in the UK Aeronautical Information Publication. 

    As at January 2019 the following UK airports are in scope of the second criterion:

    • Aberdeen
    • Belfast City
    • Belfast International
    • Benbecula
    • Biggin Hill
    • Birmingham
    • Blackpool
    • Bournemouth
    • Bristol
    • Cambridge
    • Campbeltown
    • Cardiff
    • Carlisle
    • City of Derry
    • Cranfield
    • Doncaster Sheffield
    • Dundee
    • Durham Tees Valley
    • East Midlands
    • Edinburgh
    • Exeter
    • Farnborough
    • Glasgow
    • Gloucestershire
    • Hawarden
    •  Humberside
    • Inverness
    • Islay
    • Kirkwall
    • Leeds Bradford
    • Liverpool
    • London City
    • London Gatwick
    • London Heathrow
    • London Luton
    • London Southend
    • London Stansted
    •  Lydd
    • Manchester
    • Newcastle
    • Newquay
    • Norwich
    • Oxford
    • Prestwick
    • Scatsta
    • Southampton
    • Stornoway
    • Sumburgh
    • Wick



    If an airport is not listed, then the PPR process cannot apply to it. However, the list could change over time (the above information was compiled in January 2019).

    Although Northolt does have a published SID, it is excluded on the basis that a change proposed by or on behalf of the Ministry of Defence is specifically excluded from the scope of a relevant PPR. 

    On 31 March 2017 we published revised guidance material on the new process for consultation. This will replace our old process document, CAP 725. View our consultation and responses we received (consultation now closed). Our detailed analysis of all of the responses and recommendations we received is available in our report Outcome of the CAA consultation on draft airspace design guidance (CAP 1615).

    The consultation documentation comprised the draft guidance document itself, a draft environmental technical annex to the guidance, a separate document about a new category of airspace change (known as 'Tier 2') which the Government discussed in its consultation, and a pdf version of the CAA's consultation document and questions.

    Our 2017 consultation on the guidance material followed a consultation we held in 2016 on the principles of the new process and an independent review conducted by consultants Helios in 2015.

    See the Related Information below for older information about why we decided to change the process.


    Information about arrangements for transitioning to the new process is available on the transitioning process page on our website


    We have produced a number of policy statements which include technical guidance and information on the process to be followed for certain types of airspace change. The technical information remains valid and should continue to be followed. However, following the publication of the new airspace change process, some process information (that which relates solely to the airspace change process and how it should be followed) in these policy statements is no longer valid and should be disregarded. Please contact the CAA for further information. The guidance on our airspace change process and how it applies to any request for a change to airspace design is now all located in one place: in CAP 1616. In due course we will complete a full review of these policy statements and update them to reflect the new process.