Why are so many airline check-in counters idle so often?

It’s not that they are idle per say, they actually fill up and get busy quite often when there is a flight that is ready to take off. The thing with airlines is that they are busy around the time flights are leaving, and like any other business, they have busy times and slower times. Airlines often use queue systems, mainly stanchions and retractable belt barriers are used to create the waiting lines.

Note: this answer is a bit speculative, based on general economic principles rather than any specific knowledge about the airline industry.

But I think your question may be based on the sunk cost fallacy.

My understanding is that counter space is allocated to airlines as part of their lease agreements with the airport, and that these are fairly long-term agreements (several years). So the airline has already paid for the counter space whether it uses it or not. “Wasting” that real estate on any given day doesn’t actually cost them anything.

However, paying hourly employees to staff counters that they don’t really need definitely costs them money.

Hence, the airline has a clear incentive to staff only as many counters as they need to provide whatever level of customer service they consider adequate – certainly no more than that.

You might ask why they don’t raise their customer service targets and staff more counters for that reason. Presumably they have decided that would not generate enough extra revenue to offset the costs. I think evidence within the industry tends to suggest that customers are far more sensitive to fares than to customer service – so even if one airline had shorter lines than their competitors, it might not win them a significant amount of extra business, or enough customer preference to allow them to raise their fares above their competitors.

You might ask why, if an airline rarely staffs all its counters, why it would pay to lease so many. I suspect that counter real estate may not be as “valuable” as you think. Empirical observation suggests that airports have many more counters than airlines actually want to use, so supply and demand would suggest that they should be relatively cheap to the airline. Hence the airline may be able to secure a large number of counters at relatively low extra cost. That cost may be justified just for the rare occasions when they are all needed (e.g. holidays and other peak travel times), and at other times they will simply sit idle because, as above, it is not worth the cost of staffing them.

You might ask why, if counters are such low-value real estate, why airports build them with so many. I would guess this is because most of them were built quite some time ago, when airline customer service levels were higher. For instance, the newest major airport in the US is 20 years old this year.

Check in counter and aircraft parking gates at airports are usually provided in as copious quantity as is possible for the space. This allows for maximum usage during peak arrival/departing times slots and allows space for expansion in terms of number of flights/airlines serving the airport.

Airlines that make frequent flights to an airport tend to have specific gates and counters assigned to them. Airlines that make only one or two flights often share a gate and counter.

Airlines like consistency for their regular customers, so at XYZ airport, their frequent flyers would know to always go to counter 24-29 and their flight crew will know that likely they will be parking at B concourse.

At airports where the ground staff are contracted through the airport, specific workers handle specific airlines. While the check in procedures are similar, each airline has it own in house rules for dealing with Elite flyers, baggage, upgrades, etc. And it would be tough for each contract worker to know every airline’s rules (and time consuming for them to look it all up).

While there are times when the airport seems empty, there will also be times when every parking gate will be full and every check in counter buzzing with activity. And because airline scheduling is dependent on many factors other than airport slots, the airport managers can not really force airlines to fly in at times that make better use of the counter space.