Plain English Meaning

A row of flashing lights leading up to the runway that helps a pilot find and line up with the runway when approaching to land, especially in poor visibility. The lights flash one after another toward the runway, like an arrow pointing the way in.

Full Definition

A simple approach lighting system used at non-precision instrument runways, consisting of seven omnidirectional flashing lights — five spaced along the extended runway centerline outward from the runway threshold, and two more positioned on either side of the runway threshold itself. The lights flash in sequence from the outermost light toward the runway, helping the pilot identify the runway and align with its centerline during the final stages of an approach.