What is the definition of "Clear" cloud cover?

The definition of "Clear" cloud cover refers to a condition where there are no clouds present in the sky, allowing for unobstructed visibility. This term is important for flight operations, especially for unmanned aircraft, as cloud cover can affect both the safety and effectiveness of a flight mission. Clear conditions mean that pilots can see the terrain and other airspace users without any obstructions, which is essential for maintaining situational awareness. In aviation weather reports, "clear" indicates optimal conditions for flying.

The other options refer to varying degrees of cloud cover, which would not meet the criteria for being classified as "clear." The presence of clouds, even in small amounts, can impact visibility and the overall flying environment, hence why these alternatives do not align with the definition of clear cloud cover.