What is the least serious category of runway incursions?

The least serious category of runway incursions is Category D. This classification encompasses situations where there is no immediate safety risk but where aircraft or vehicles enter a runway without proper clearance or authorization, resulting in a potential conflict. Examples may include minor deviations that do not pose an imminent threat to operations, such as a vehicle crossing a runway while an aircraft is in a safe distance or during an idle phase.

Understanding this categorization is important for recognizing how different types of incursions can affect airport safety and operations. Category D incursions are typically monitored and may involve follow-up procedures to ensure that the operators receive the necessary training or awareness to prevent similar occurrences in the future.