Plain English Meaning

A set of lights next to the runway that tells you, just by their colour, whether you're coming in too high, too low, or just right.

Full Definition

A ground-based system of lights placed beside the runway that gives pilots a visual indication of whether they are on, above, or below the correct approach path to the landing threshold. A standard VASI uses two bars of lights; the colour combination seen by the pilot (red and white in various arrangements) shows the aircraft's position relative to the proper glide path.

Context Anchor

Seen beside some runways during landing, especially when the pilot is using outside visual references to judge the .