For my work as a safety manager and investigator for ATC incidents it is vital to understand why practitioners make their decisions, why their actions make sense to them, whether the outcome later on is positive or negative. To see their work through their eyes helps to support the system, ensuring that things go right while also preventing things from going wrong. What makes sense to one controller or engineer most of the time usually makes sense to others at the time.

Our controllers make decisions based on their local rationality and in 99.9% the outcome is positive. One example was when a controller came to us and reported that he had taken an aircraft below the minimum radar vectoring altitude (MRVA). This is normally prohibited. The procedures do not allow this because the MRVA is the lowest safe altitude, which is clear of obstacles. Within controlled airspace in most cases this absolutely makes sense.