What is the primary requirement for flying a UAS at night?

The primary requirement for flying a UAS (Unmanned Aircraft System) at night is that the UAS must have proper lighting for visibility. This requirement is crucial because, during nighttime operations, the pilot must be able to see the UAS to maintain visual line of sight and ensure safe operation. The lighting helps both the pilot and others in the vicinity to be aware of the drone's position, direction, and altitude, which is essential for avoiding collisions and ensuring safe navigation.

While other options might suggest additional considerations, such as the presence of a visual observer or special training, the most fundamental safety requirement is the presence of adequate lighting. This is in accordance with regulations set forth by the FAA, which mandates that UAS operating at night must be equipped with lighting that enables the pilot to maintain visual line of sight, thereby ensuring operational safety.