Political Restrictions
Detailed Description
Prevent airlines from operating in violation of the generally accepted freedoms of the air or to nations where they would be prohibited due to the current political climate.
Context
This would, for example, prevent foreign airlines from operating domestic routes in a given nation, which often stifles new airlines which are trying to find their feet, particularly in large and/or remote countries.
Another effect would be that an airline cannot simply fly between any 2 nations, preventing monopolism or uncontrolled expansion and keeping the game competitive.
An exception may be, for example the EU, where there is a single aviation market, allowing airlines to operate within other countries. However, this should be treated as a perk of being based in a specific location, rather than being a principle of the entire game, as it is now.