What factors determine the size of holding pattern protected airspace?

The size of the holding pattern protected airspace is primarily influenced by altitude and airspeed. As an aircraft enters a holding pattern, the configuration of the airspace around the holding fix must provide adequate separation from other aircraft and obstacles, while allowing the aircraft to safely conduct the holding maneuver.

At higher altitudes, the controlled airspace can be larger since the distances that aircraft can travel during turns and while maintaining safe separation from other aircraft increase. Similarly, the speed of the aircraft is a critical factor; faster aircraft require more space to maneuver safely than slower ones. Therefore, the combination of these two elements—altitude and airspeed—directly determines the dimensions of the holding pattern airspace required for safety and efficiency.

Other factors like weather and visibility, air traffic density, and geographic location may influence operational considerations but do not directly define the protected airspace of a holding pattern as fundamentally as altitude and airspeed do.