How is the nighttime period defined for ATC time?

How is the nighttime period defined for ATC time?

• A. The time between evening civil twilight and morning civil twilight
• B. The time between midnight and noon
• C. The time from sunrise to sunset
• D. The time from noon to midnight

Answer: (A)

Nighttime for ATC time uses lighting conditions defined by civil twilight, not a fixed clock time. It’s the interval from the end of evening civil twilight to the start of morning civil twilight, which occurs when the sun is more than about 6 degrees below the horizon. In practical terms, this means night spans the period after sunset until before sunrise, including any nautical or astronomical twilight that occurs during that span. This definition aligns with actual visibility and lighting needs for aviation operations. The other options rely on fixed clock times or standard daylight concepts that don’t reflect how ATC distinguishes night based on sun position and illumination.

Nighttime for ATC time uses lighting conditions defined by civil twilight, not a fixed clock time. It’s the interval from the end of evening civil twilight to the start of morning civil twilight, which occurs when the sun is more than about 6 degrees below the horizon. In practical terms, this means night spans the period after sunset until before sunrise, including any nautical or astronomical twilight that occurs during that span. This definition aligns with actual visibility and lighting needs for aviation operations. The other options rely on fixed clock times or standard daylight concepts that don’t reflect how ATC distinguishes night based on sun position and illumination.