What is the purpose of Runway End Identifier Lights (REILs)?

Runway End Identifier Lights (REILs) serve the crucial purpose of indicating the end of the runway. These lights are located at the runway's threshold, typically positioned on either side, and are designed to provide visual cues to pilots, especially during low visibility conditions. By illuminating the end of the runway distinctly, REILs help in establishing a clear reference for the landing pilot, enhancing situational awareness, and aiding in a safe and precise landing approach.

While other lighting systems serve different functions—such as alignment indicators or obstruction markers—REILs specifically focus on marking the termination of the runway. This is particularly important when a pilot is executing a landing, as the lights signal when the usable runway length is completed, helping to prevent landings that may extend beyond the runway limits.