FAA Ground School Practice Test

What is the definition of nighttime in aviation?

1. The time immediately following sunset until sunrise

2. The time between the end of evening civil twilight and the beginning of morning civil twilight

3. The hours of darkness where no flight is permitted

4. When aircraft lights must be turned on

The correct answer is: The time between the end of evening civil twilight and the beginning of morning civil twilight

The definition of nighttime in aviation is specifically tied to civil twilight, which marks the transition times between day and night. It is defined as the period when the sun is below the horizon and light conditions are low enough that artificial lighting becomes necessary for safe operation. Choosing the period between the end of evening civil twilight and the beginning of morning civil twilight precisely reflects the conditions that define nighttime. During this period, pilots must adhere to certain regulations regarding the use of lights and are required to follow specific operational protocols that apply only during nighttime. In contrast, the other options do not fully encapsulate the regulatory definition of nighttime. The time immediately after sunset until sunrise could imply a longer duration than the specific operational definition. The idea that no flight is permitted during darkness is inaccurate, as there are flights that occur at night under proper regulations and conditions. Likewise, while aircraft lights are mandatory during nighttime operations, this requirement alone does not define the entirety of nighttime in aviation. Thus, option B accurately describes the specific regulations associated with nighttime operations in aviation.