What indicates that a runway is contaminated?

The indication that a runway is contaminated primarily revolves around the degree of coverage and type of contamination present. In this context, the correct answer reflects a specific standard for evaluating runway conditions. When more than 25% of the runway is covered by 1/8 inch of standing water or similar conditions, it demonstrates a significant potential reduction in the runway's friction, increasing the risk of hydroplaning and other adverse effects on aircraft performance during landing and takeoff.

The reference to 1/8 inch of standing water is significant as it provides a clear threshold that signals a safety concern for pilots and ground control when assessing runway conditions. This standard helps in formulating operational decisions and alerts necessary authorities to provide appropriate advisories.

The other choices, while they relate to runway conditions, do not capture the critical thresholds that specifically define contamination status as outlined in aviation safety guidelines. For instance, a completely snow-covered runway indicates it is not usable but does not describe a measurement of water accumulation that directly impacts aircraft handling. Similarly, coverage by 25% standing water does not meet the threshold that heightens safety concerns. The presence of mist or fog does not pertain to the physical condition of the runway's surface but rather visibility, which is an entirely different safety