Why does a clean aircraft formation create a stronger vortex?

A clean aircraft formation creates a stronger vortex primarily because of the more square footage of wing area. When aircraft are in a formation, particularly during takeoff and landing, the wings generate lift through their design and surface area. The larger wing area contributes to increased lift generation, which in turn influences the airflow patterns around the aircraft.

This stronger airflow creates more defined and powerful vortices at the wingtips. Vortices are a natural byproduct of lift generation, created by the difference in pressure above and below the wing. A larger wing area typically leads to stronger lift production, amplifying the effects of the pressure differential and resulting in more pronounced vortex formation.

The other options, while they relate to the overall dynamics of flight, do not inherently lead to stronger vortices in the same direct manner as an increase in wing area. For instance, less drag on the wings and higher speed can influence overall performance but do not necessarily relate to the vortex strength caused by wing area dynamics. Similarly, flying at a lower altitude does not inherently increase vortex strength; it may affect other flight characteristics without directly affecting vortex intensity associated with formation flying.