Plain English Meaning

Bright, easy-to-spot lights — like the rotating airport beacon, runway lights, or other strong lights near the field — that a pilot uses at night to estimate how far they can see.

Full Definition

Conspicuous illuminated features at or near an airport — such as airport beacons, approach light systems, runway edge lights, lighted obstructions, or distinctive city lights — that a pilot can identify at night to determine flight visibility. At night, when daytime reference markers cannot be seen, flight visibility is judged by the greatest distance at which these prominent lighted objects can be clearly seen and recognized.

Context Anchor

Seen in visibility discussions, especially when comparing daytime visibility references with nighttime visibility references.