What is the significance of the 30-minute periods before and after sunset?

The significance of the 30-minute periods before and after sunset marks the beginning and end of night operations. During these times, the lighting conditions change significantly, impacting visibility and the ability of pilots to operate safely. Specifically, civil twilight occurs roughly 30 minutes before sunrise and after sunset, during which time it may still be partially light, but operations may require different levels of caution and procedural adherence compared to daylight operations.

Recognizing these periods is crucial for aircrew training and operational planning since night operations often involve additional risks and require specific protocols to ensure safety. Understanding the transitions in visibility and lighting helps pilots prepare for the challenges associated with flying in conditions where natural light is diminished.