What does a large white X symbol signify on a runway?

A large white X symbol on a runway indicates that the runway is unusable. This marking is used to alert pilots that the runway should not be used for takeoff or landing due to various reasons, such as maintenance work, unsafe conditions, or structural issues. The presence of this symbol serves as a clear and unmistakable warning that the surface is not safe for aircraft operations.

In aviation, it is crucial for pilots to receive clear and accurate information regarding runway status to ensure safety. The X specifically conveys a definitive message that the runway is not in service. By marking a runway with a large white X, air traffic control and airport operations can effectively communicate this status to pilots, preventing potential accidents or incidents.