When can aircraft be cleared to hold over different fixes at the same altitude?

Clearing aircraft to hold over different fixes at the same altitude is permissible when the holding pattern airspaces do not overlap. This is crucial in order to ensure safety and maintain separation between the aircraft. Holding patterns are basically predetermined flight paths that aircraft follow while waiting for further instructions from air traffic control, and these patterns require a certain amount of airspace.

If two holding patterns were to overlap, there could be a risk of conflict between the aircraft, leading to potential safety issues. Therefore, it is essential to ensure that the lateral boundaries of each holding pattern are sufficiently separated. This allows each aircraft to operate within its designated airspace without interfering with the other, which is why the condition of non-overlapping airspaces is the correct and necessary guideline for this scenario.