If OP (based in GVA) has to use data from EU (or even DACH) airports, that data will not be of any use.

I wouldn't automatically assume that airports make losses. The flights still have to leave at some point as you can only substitute only a small number of flights. A DUS-FRA can easily be replaced by a bus/train. It's a little more difficult to make a bus/train go TATL.

Furthermore, it's probably useful to differentiate between punctual cancelations (individual flights) and massive cancelations (weather, volcano ashes, etc...).

In the former situation, chances are that airports and their merchants are going to make a little more profit (people have to eat/drink, be entertained and sometimes even have to sleep somewhere. Given that the stranded PAX make up only a marginal fraction of all passengers, an airport can expect that there will be no additional costs (such as garbage disposal, cleaning, electricity, wear and tear of seats in the departure hall, etc...) Conclusion: More consumption = more money).

In the latter situation, profits might be only marginal. There will be a lot of stranded passengers, that airlines are going to accommodate. Airports and Airlines usually set up camp beds (as hotels can't simply stomach the huge demand). The passengers need 24/7 help, which is at least unusual for most European airports that close down for the night. The increased number of passengers in the terminal are going to create more garbage and sanitary installations have to be cleaned at higher rates to maintain the service level, we are used to. Conclusion: A profit would seem surprising.

I would imagine that both airlines and airports take this risk into account and make adequate budgetary appropriations for such cases.