A Category D Incursion is defined as:

A Category D Incursion refers specifically to an incident on the airport's movement area which does not immediately compromise safety but still indicates a deviation from standard operating procedures. This can occur in scenarios where an aircraft or vehicle inadvertently enters a runway or taxiway that has not been authorized, yet no immediate action is required to prevent a collision.

This category helps to categorize incursions based on their severity and the urgency of action needed. By identifying a Category D Incursion as one with no immediate safety consequences, it emphasizes that while the situation is not critical at that moment, appropriate measures must still be taken to review and address the conditions that led to the incursion, ensuring that safety protocols are reinforced.

Other options describe scenarios that either involve immediate safety hazards or do not accurately characterize the essence of a Category D Incursion, highlighting the importance of distinguishing between levels of risk in airport operations.