What factors influence the spacing between arriving aircraft?

The spacing between arriving aircraft is influenced significantly by prevailing weather conditions and aircraft size. Weather conditions, such as visibility and wind, directly affect an aircraft's approach and landing capabilities. For instance, in reduced visibility due to fog or rain, greater spacing is required to ensure that each aircraft can maintain a safe distance and execute approach procedures effectively. Similarly, aircraft size contributes to spacing because larger aircraft need longer distances to slow down and stop compared to smaller aircraft. This means that air traffic controllers must account for these factors to maintain safe and efficient landings.

Considering the other options, while runway length and surface type are important for overall operations, they do not directly influence the spacing of aircraft during arrival. Time of day and air traffic volume can affect the workload and traffic, but they are more secondary factors compared to the immediate impacts of weather and size on spacing. Fuel levels and flight paths are relevant to operational planning but do not directly dictate the spacing needed for arriving aircraft, which is rooted more in safety and performance characteristics influenced by weather and size.