Why Twilight Can Be a Complicated Time for Pilots

Do you know the difference between civil twilight, nautical twilight and astronomical twilight?

Peter Garrison

Thursday, February 15, 2018 at 08:00 PM ET

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Twilight is partitioned into three zones: civil, nautical and astronomical. Pexels

Key Takeaways:

Pilots often succumb to poor judgment when attempting night flights, especially in challenging conditions like dense fog or to unlighted airstrips, leading to fatal accidents.
The article highlights multiple incidents where pilots crashed into obstacles, primarily trees, due to flying at dangerously low altitudes in total darkness, often after astronomical twilight.
Spatial disorientation, such as the "black-hole illusion," can cause pilots to fly too low on final approach, even when instrument guidance (like a PAPI) is available and functional.
These accidents frequently involve pilots with insufficient or outdated night flying experience, underscoring the critical need for proper judgment and adherence to safety protocols.

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Twilight is a complicated thing. It is partitioned into three zones. There is civil twilight, which lasts from sunset to when the center of the sun is 6 degrees, or about 12 solar diameters, below the horizon and things can no longer be clearly seen.

Then comes nautical twilight, which ends when the center of the sun is 12 degrees below the horizon and a seaman no longer discerns the break between the western sea and the sky. Finally, astronomical twilight ends when the sun is 18 degrees below the horizon, leaving the sky black enough for the inspection of distant galaxies.