What visual limitation must a UAS operator adhere to during flight?

A UAS operator must ensure that the aircraft remains visible to them at all times during flight, as this is critical for maintaining situational awareness and ensuring safe operation. This requirement is an essential aspect of the rules for remote piloting, as it allows the operator to effectively monitor the aircraft's position and surroundings, avoiding potential collisions with other aircraft, obstacles, or individuals on the ground.

By being able to see the UAS directly, the operator can react promptly to any unexpected situations or changes in the environment. This visual line-of-sight requirement emphasizes the importance of maintaining control and responsibility over the UAS, aligning with safety regulations enforced by aviation authorities.

In contrast, the other options may contain components of operating procedures but do not address the critical aspect of visual control during flight, which is fundamental to safe UAS operation.