What does "visual line-of-sight" (VLOS) refer to in UAS operations?

Visual line-of-sight (VLOS) in UAS operations specifically refers to the requirement for the operator to maintain direct visual contact with the unmanned aircraft system (UAS) throughout the entire flight. This means that the operator should be able to see the drone with their own eyes without the aid of any visual enhancement devices, such as binoculars or viewing monitors. Maintaining VLOS is crucial for ensuring safety, as it allows the operator to monitor the aircraft's position, altitude, and any potential obstacles or other air traffic.

This concept is important in regulatory frameworks governing UAS operations, as it helps to minimize the risk of collisions and ensures that the operator can respond to any issues that may arise during flight. In contrast, other options such as altitude restrictions, pre-planned flight paths, or using onboard cameras pertain to different aspects of UAS operation but do not define the essence of visual line-of-sight.