> What if you collect too much?

You lower fees the next year.

Then if you collect too little? Where does the excess come from? Do you keep the fees high and pay that back next year? Do you account for inflation or charge points?

Is there some reason you _don't_ want this system to have slightly more funding than it "needs?"

Nav Canada, the non-profit which runs Canada's ATC, charges user fees which they adjust every so often, but they also have buffer/contingency funds.

Quarterly/annual financial reports are available at their site:

* https://www.navcanada.ca/en/corporate/investor-relations/fin...

* https://www.navcanada.ca/en/corporate/service-charges.aspx

It is worth noting that Nav Canada also has controller shortages. Privatization is not really correlated with with better outcomes for ATC.

https://globalnews.ca/news/11354998/air-traffic-controller-s...