A runway is considered contaminated when more than what percentage of the surface area is covered by certain conditions?

A runway is classified as contaminated when more than 25% of its surface area is covered by particular factors such as water, snow, ice, or slush. This threshold is significant because once contamination reaches this level, it can considerably affect the performance of aircraft during takeoff and landing operations. Contamination can lead to reduced friction between the tires and the runway surface, increasing the risk of hydroplaning or losing braking effectiveness. Understanding this percentage is crucial for pilots and air traffic control in assessing runway conditions and ensuring safe flight operations.