For every Airprox incident assessed, the Board determines one or more causal factors. These tell us why events started in each instance and signpost the lessons to emerge. Attention paid to 'cause' is worthwhile because it is likely to deliver and promote better prevention.
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:
Guidelines on cause and risk June 2016