Is airspace more crowded on days following cancellations or a large number of delays? I am looking at some data form the BTS and trying to understand some spikes in month to month Volume delays. From my understanding a Volume delay is due to the volume of airplanes, causing the ATC to manage more take offs and landings and therefore slowing down the whole process.

My problem is that for volume delays bts only provides monthly aggregates. So I have data with a spike for Volume but the number of flights on that same month is normal or sometimes less than average. So I am assuming that something is happening at the daily level that is completely lost in the aggregation.

This all boils down to my question. If we where to quantify the capacity of the airspace around say ORD and call it X and on average the airspace is occupied with N planes, such that N &lt; X and airspace is operating at N/X capacity.

On days following mass delays or large number of cancellations, does the amount of planes in the airspace increase to alleviate the pressure of passengers who are behind schedule? or does the load factor simply increase?

For examples say that on average airspace at ORD operates at 75% capacity, then one day you have some event that causes a lot of delays and cancellations. Do the following days operate at say 90% airspace capacity to help relive that congestion? or do they still operate the same number of planes but those planes are simply almost guaranteed to be full.

All summed up, would a spike in delays for some reason other than plane volume result in a spike in volume delay in the following days as they deal with the extra passengers?

Sorry if this question is worded strange, I had a hard time putting it down in writing. If its unclear let me know and I'll try to clarify.
I would say generally no, because there are only so many landing slots available at busy airports and airlines frequently substitute larger aircraft to clear up a passenger backlog.