Challenges of the visual line of sight operations of unmanned aerial vehicles

The following question often emerges: what is the maximum distance during a visual line of sight (VLOS) operation between the remote pilot and the unmanned aerial vehicle (UAV)? The answer is complex, and there is no particular number because it depends on several factors that have to be jointly taken into consideration. The generally mentioned 1 km rule is not applicable for all cases. In some cases, 1 km means the absolute maximum. However, it should be considered that in certain situations, the operation can get out of the VLOS operation limits, even if obstacles and other factors do not hinder the view of the UAV.