What is defined as "night" in aviation?

In aviation, "night" is specifically defined as the time period that begins when civil twilight ends. Civil twilight is the period when the sun is between 0 degrees and 6 degrees below the horizon, during which there is enough natural light for most outdoor activities. Therefore, the end of civil twilight marks the beginning of night, which is significant because the requirements for aircraft operations, including the need for specific lighting, change at this time.

Understanding this definition is crucial for pilots and flight planners as it affects flight planning, regulatory requirements, and operational procedures. Knowing when night begins influences whether certain equipment needs to be used, and it also has implications for maintaining visual flight rules (VFR) versus instrument flight rules (IFR).

Other provided options do not accurately capture the aviation definition of night. While the time between dusk and dawn encompasses the entire night, it is not precise enough for aviation standards. The concept of a period when no flights are allowed is not related to the definition of night in itself, as flights can occur during night hours under certain conditions. Lastly, the time between morning and evening civil twilight does not align with the standard definition of night, as it includes periods of both day and twilight rather than focusing solely on night.