• Rationale

    Intelligence sources  show that Mid-Air Collision (MAC) remains a key risk in UK airspace, because of our busy, complex airspace serving significant military and general aviation (GA) activity (including sporting, leisure and business jets).  The airspace continually evolves and draws together inputs from multiple stakeholders and is currently the subject of extensive ongoing change under the Single European Sky programme.

    In 2016 there were 253 Airprox reports, of which 111 were considered risk-bearing.  Of these risk bearing events, the majority involved general aviation, followed by those involving military aircraft; commercial air transport were involved with 48 of those events.  It is worthy of note that the number of reported airproxes involving drones is rising most quickly.  Alongside Airprox, NATS has confirmed that over 1,000 airspace infringements occur each year and this figure sets that issue as the highest risk event that NATS face at this time.  As traffic levels increase it is important that we recognise the more likely need for focussed intervention, to ensure that the potential for mid-air collision does not increase.

    MAC is a complex and long-term challenge and as such the MAC Programme aims to reduce the risk of mid-air collision by pursuing targeted and continuous improvements in systems, cultures, processes and capability. The MAC programme works closely and collaboratively with the UK Airprox Board, UK Flight Safety Committee, CAA UAS Programme, Military Aviation Authority and industry stakeholders to understand and assess risk and identify effective and collaborative mitigations. This programme also meets the European Plan for Aviation Safety (EPAS) requirement for Member States to address MAC in their safety plans.

    EPAS requires Member State National Aviation Authorities to:

    • Play the leading role in establishing and promoting local implementation priorities and actions to manage the risk of general aviation airspace infringement;

    • Implement the 2014 EASA recommendations on the loss of radar detection, and to consider implementation of other mitigation techniques against loss of detection of aircraft as a result of SSR over interrogation.


    • Mitigate the risk of MAC for consumers on UK aircraft operating both within UK and in overseas airspace.

    • Use multiple data sources, collaboration with industry and the exchange of information across national and international aviation sectors to identify and address the most significant MAC causal factors.

    • Employ a range of means including best practice recommendations, regulatory change, training and improved information sharing to mitigate the MAC risk.

    • Under the direction of the MAC Programme Board and scrutiny of the MAC Challenge Group, Industry groups (Airspace Infringement Working Group, Local Airspace Infringement Teams, Level Bust Working Group and the Electronic Conspicuity Working Group) are established to monitor trends and highlight areas to focus activity on MAC in a holistic and coordinated strategic, operational and tactical manner. 


    The MAC Programme uses themes around People, Aircraft & Technology and Airspace & Air Traffic Management, and will undertake specific activity on airspace infringements, level busts, TCAS resolution advisory events, and visual and electronic conspicuity.

    The programme will continue to:

    Manage data on MAC events and use this smartly to steer action and mitigation strategies with industry collaboration.

    Progress close cooperation and coordination with the CAA UAS Programme and UKAB.

    Enhance mechanisms to publish related information and action through the CAA-hosted Airspace Safety Initiative (ASI) website.

    Work closely with technology manufacturers to encourage the development and deployment of conspicuity devices which are interoperable, practical installations and affordable.

    Monitor the effectiveness of published guidance on a new industry standard for low-cost electronic conspicuity devices for use on light aircraft.

    Contribute to the update and accessibility of the recently published CAP 1535 The Skyway Code to act as a guide to airmanship and best practice for pilots in order to supplement the work of the AIWG.

    Continue education and safety promotion in respect of moving-map technology for enhanced situational awareness. 

    The programme has:

    • As part of its five-point plan to address Airspace Infringements, the MAC has successfully refocused the cross-industry Airspace Infringement Working Group to concentrate on specific issues and projects, such as developing and enhancing the work of Local Airspace Infringement Teams. The MAC has also made great strides to enhance the CAA’s Infringement Oversight and Enforcement work to improve the online infringement tutorial and test and to introduce an airspace infringement awareness course to be attended by infringing pilots as required by the CAA. Better information will also be made available to flight training instructors and to those parties engaged in two yearly competency checks.
    • Expanded the Terms of Reference of the MAC Level Bust Working Group to effect the analysis of incidences of Traffic Alert and Collision Avoidance System Resolution Advisory  (TCAS RA), with close cooperation between MAC and related UK and International stakeholders established.