Which of the following factors is essential for the safe operation of a sUAS?

Ensuring visual line of sight at all times is crucial for the safe operation of a small Unmanned Aircraft System (sUAS). This practice allows the operator to effectively monitor the sUAS's position, altitude, and trajectory, which is vital for avoiding collisions with other air traffic, obstacles, or people on the ground. Maintaining visual line of sight also helps in responding promptly to any emergencies or unexpected situations, thus enhancing the overall safety of the flight operation.

While flying only during the daytime can contribute to safety by improving visibility, and automated systems can assist in operations, they do not replace the need for maintaining a clear line of sight with the aircraft. Additionally, flying without restrictions from traffic is impractical as it disregards the necessary regulations that guide safe operations within shared airspace. These regulations are in place to ensure that all aerial activities are conducted safely and responsibly.