Definition
A visual cue used by pilots flying at night to detect the presence of clouds when the clouds themselves cannot be clearly seen. Clouds at night are typically identified by the absence of stars in part of the sky, by a halo or diffused glow around lights on the ground or around the moon, or by the aircraft's position lights reflecting off nearby cloud surfaces.
Plain English
At night you usually cannot see clouds directly. Instead, you spot them by what they hide or how they scatter light — stars disappearing behind them, a fuzzy ring around the moon or ground lights, or your own aircraft lights bouncing off them.
Context Anchor
Used in night flying, especially when judging whether the path ahead is clear and when comparing what is seen outside with the reported weather.
Why Pilots Care
Unintentional entry into clouds at night removes all visual references and frequently leads to spatial disorientation and loss of control.
Grounding Statement
Imagine flying on a clear night with stars across the whole sky, then noticing a black patch where stars have vanished — that patch is almost certainly a cloud.
Intuition Check
Do not assume a dark area ahead is clear air. At night, an unlit cloud can look like open sky.
Example Sentence 1
On the cross-country flight, the pilot noticed a halo forming around the city lights below and realised they were approaching a layer of clouds.
Example Sentence 2
Before departure the instructor reminded the student to watch for clouds at night because visual references disappear quickly.