After months of behind the scene work, days of research and many overpriced energy drinks, I finally decided to find and replace 29 country codes. At the mere price of national identity you can now operate domestic flights within the Schengen zone.
I have removed all national entries in the CountryData.json and replaced it with one new country; the “European Union”. At the same time I have searched and replaced all country codes in the AirportData.json with the new “EU” country code.
Download & Install
Download the two files and replace the existing files in
Steam\steamapps\common\Airport CEO\Airport CEO_Data\DataFiles\GameData
This will bork any existing savegame and this step might need to be repeated every single time the game updates. To un-bork existing savegames open this file
\AppData\Roaming\Apoapsis Studios\Airport CEO\Saves\TestAirport\GameData.json
and update the countryCode and countryName values to “EU” and “European Union”