Definition
A row of high-intensity sequenced flashing white lights installed in the approach lighting system of an instrument runway, extending outward from the runway threshold along the extended centerline. The lights flash in rapid sequence toward the runway, giving the appearance of a ball of light traveling toward the threshold to help the pilot visually align with the runway during the final stages of an instrument approach.
Plain English
A line of bright flashing white lights placed in front of the runway that pulse one after another toward the runway, creating a moving streak of light that points the pilot straight to where they should land.
Context Anchor
Seen during night or low-visibility approaches, especially when approaching a runway equipped with approach lights.
Derivation
The name describes the function: the lights indicate the alignment of the runway. 'Indicator' comes from the Latin 'indicare,' meaning 'to point out' — these lights literally point the pilot to the runway.
Why Pilots Care
They give precise visual guidance for runway alignment, helping prevent landings that are offset from the centerline in low visibility or at night.
Analogy
Think of the chasing arrows on a freeway off-ramp at night — each one lights up in sequence, pulling your eye toward where you need to go.
Intuition Check
Do not confuse these with lights on the runway pavement. Runway Alignment Indicator Lights are mainly approach lights that help you line up before reaching the runway.
Example Sentence 1
As we descended through the cloud base, the runway alignment indicator lights flashed clearly ahead, leading us straight to the threshold.
Example Sentence 2
Even in reduced visibility the steady line of Runway Alignment Indicator Lights allowed a smooth transition to the runway surface.