When running some Tracon!2012 scenarios (default or add on sectors) I observed that many flights were missing and were not being simulated despite being listed in the respective database files.
I checked the game.logs with the following result:
In almost all of my logs I found many entries labelled Unknow airport: xyz(IATA) ICAO not found!
Here are some hints on what may cause such entries:
the database file schedule.txt contains one or more semicolons instead of comma
the database file schedule.txt contains one or more IATA airport codes which are not defined in the airports datase