What does a painted or lighted X on a runway signify?

A painted or lighted X on a runway signifies that the area is closed to aircraft and vehicle operations. This marking serves as a clear visual indication to pilots and ground crews that the runway should not be used for takeoff, landing, or taxiing. This is particularly important for safety, as it helps prevent accidents that could result from an aircraft inadvertently attempting to use an unsafe or non-operational runway.

This marking is standard across aviation practices, aligning with regulations to ensure consistent communication about runway status. Pilots are trained to recognize these symbols, which are crucial for effective air traffic management and airport operations. The presence of the X communicates an immediate need for avoidance, underscoring the importance of obeying all runway markings.