• Rationale

    Intelligence sources continue to 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, drawing together inputs from multiple stakeholders, and is currently the subject of extensive ongoing change under the Single European Sky programme, Future Airspace Strategy and as preparatory work in realising the National Policy Statement on airport capacity.

    In 2016 the UK Airprox Board (UKAB) assessed 265 Airprox, of which 171 were aircraft-to-aircraft encounters and 94 involved drones/Small Unmanned Air Systems (SUAS). Of the 171 aircraft-to-aircraft incidents, 58 (34%) were assessed as risk-bearing events where safety was not assured (Risk Categories A & B). Of these risk bearing events, the majority involved general aviation, followed numerically by those involving military aircraft. Commercial air transport was involved in 48 events with SUAS, and one aircraft to aircraft event.

    It is worth noting that the number of reported Airproxes involving drones/SUAS is rising most quickly, with commercial air transport reporting most frequently in this area. Alongside Airprox reports, NATS has confirmed that, from their data interpretation, over 1,000 airspace infringements occur each year; this figure sets infringements 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 focused intervention by all stakeholders, to ensure that the potential for mid-air collision does not increase.

    MAC is a complex and long-term challenge to all stakeholders and as such the current MAC Programme aims to reduce, by regulatory action, the risk of mid-air collision by pursuing and encouraging targeted and continuous improvements in systems, cultures, operational processes, aiming to evolve and embed current MAC Programme actions into routine SARG business and regulatory processes (i.e. Business As Usual) to address ongoing and newly identified MAC risks.

    The MAC programme stakeholders work 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 mitigation. This collaborative approach in the UK meets the European Plan for Aviation Safety (EPAS) requirement for Member States to address MAC in their safety plans.

    The current MAC Programme Board (MAC PB) provides SARG with a MAC Data Observatory function, where Key Indicators, trend analysis data and causal factor information is received, monitored and considered. Trend deviation alerts and possible intervention actions are identified by the MAC PB and tasked to the appropriate body for action. This MAC data and coordination function is set to continue into the foreseeable future in compliance with EPAS requirements.  

    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 external scrutiny of the MAC Challenge Group, Industry groups (Airspace Infringement Working Group, Local Airspace Infringement Teams, Level Bust/TCAS RA 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 undertaking 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 evidence 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. 
    • Continue to collaborate in the evolution of SARG business and regulatory processes to accommodate and address emerging and ongoing MAC risk and actions performed under SARG business as usual.
    • Ensure that MAC objectives are fully considered within the UK Airspace Modernisation Programme currently in development.

    The programme has:

    • As part of its five point plan to address Airspace Infringements, the MAC cross-industry Airspace Infringement Working Group has successfully refocused and facilitated the establishment of new Local Airspace Infringement Teams, implemented Listening Frequencies and Squawks, brought-about improvements to the Aeronautical Charts and moved towards more dynamic and clearer understanding of causal factors . The MAC has also made great strides in enhancing the CAA’s Infringement Oversight and Enforcement work to improve the online infringement tutorial and test, introducing an airspace infringement awareness course to be attended by infringing pilots.  Stability and improved proactive measures from the AIWG has enabled Airspace Infringement action to be absorbed into ‘business as usual’ mode within the remit of the AAA Capability Airspace Regulation Team. The activity is BAU, the outcomes being analysed and acted upon will continue to be Core data for the MAC program board to respond to.
    • Better information and guidance material on respective roles, obligations and expected outcomes will also be made available to flight training examiners and to those parties engaged in two yearly competency checks.  
    • MAC PB has commissioned an external body to independently poll and interview key airspace users and industry organisations and communities to identify and test the feasibility of measures to change GA Pilot behaviours and identify associated training improvements.
    • Consider in detail the effects of airspace design which has potential to cause 'pinch-points' or a 'funnelling effect' on air traffic.
    • The expanded Terms of Reference of the MAC Level Bust Working Group have been put into place to effect the close analysis of incidences of Traffic Alert and Collision Avoidance System Resolution Advisory (TCAS RA) alerts. Cooperation between MAC and related UK and International stakeholders has been established through relevant SARG Capabilities using their ‘business as usual’ processes to further examine operational scenarios with UK Airlines, ANSPs and overseas agencies to identify causal factors and other key areas for further examination.