UK Airprox Board UK Airprox Board
  • Airprox contributory factors 

    For every Airprox incident assessed, the Board determines one or more contributory factors. These tell us why events started in each instance and signpost the lessons to emerge. Attention paid to contributory factors is worthwhile because it is likely to deliver and promote better prevention of future incidents.

    Contributory factors have been developed for each of the 9 mid-air-collision safety barriers, which provide a taxonomy for assessing the contributions of both the ground and flight elements of the incident. Although there are many nuances within each Airprox, categorising contributory factors using the standardised list below provides an ability to determine long-term trends and themes. 

    UKAB contributory factors list - July 2019

    Risk ratings

    Risk level assessments are made on the basis of what actually took place and not on what may or may not have happened. There are four categories, A - D agreed at international level, and one UK category, E, as follows:

    A Risk of Collision: aircraft proximity in which serious risk of collision has existed
    B Safety not assured: aircraft proximity in which the safety of the aircraft may have been compromised
    C No risk of collision: aircraft proximity in which no risk of collision has existed or risk was averted.
    D Risk not determined: aircraft proximity in which insufficient information was available to determine the risk involved, or inconclusive or conflicting evidence precluded such determination
    E Met the criteria for reporting but, by analysis, it was determined that normal procedures, safety standards and parameters pertained

    Guidelines for UK Airprox Board Members 

    Guidelines on Contributory Factors and Risk - June 2019