Under what condition is a runway considered dry?

A runway is considered dry when 75% of its surface is clear and dry. This standard is established to ensure safe landing and takeoff conditions for aircraft. When the majority of the runway surface is free from moisture or other contaminants, it provides better traction for aircraft tires, reducing the risk of skidding or loss of control upon landing or takeoff.

In aviation terms, having a significant portion—specifically 75%—of the runway clear of moisture allows pilots and air traffic controllers to make informed decisions regarding safe operations. If a lesser percentage of the runway were dry, such as with just 50% or 100% cleared, it might not provide the necessary confidence and safety margin for efficient aircraft operation. Moisture can significantly affect performance, leading to increased stopping distances and reduced handling capabilities for aircraft. Thus, the definition of a dry runway is set to a higher threshold to prioritize safety.