Good point. There's no reason to have more planes than frequency. So in theory i can just remove the UI control of selecting number of airplanes from that perspective (and just assign the min # of airplanes that can meet the frequency set)
however, there's still some use to the UI control for selecting # of planes as airplane condition affects 2 things on a route - quality (newer plane) and how likely delays/cancellation happen, so one might still want to select a new airplane of certain model to fly a more important route
I do think the current UI of selecting airplane/frequency could be confusing
One improvement that i thought about (but not implemented) is to reduce the # of major delays/cancellation if there's more airplanes assigned to a route than it's needed. It might be coming up soon
But for now, there's not much point of assigning more airplanes than it's needed
Hope this answers your question