Something that could make operating out of different countries fun would be to have a running leaderboard of the top 10 airlines to operate in each separate country in all game worlds. This could work very similar to the current achievements, but would have a separate webpage to track it and maybe you would have an achievement added to your achievements list. This would make flying out of a smaller country more interesting as it could give an airline a target to shoot for if they don't have any active competition to keep them occupied. Or trying to become the best US or UK Airline ever might just push someone to focus on operating at their best until the very end rather than coasting to the finish line. There could even be a few different items to score on. You could go by final score, most aircraft in operation, highest company value, etc.
You would likely have to determine it according to the location of the HQ in cases like Europe. And maybe worlds where airlines can open up bases anywhere would likely have to be disqualified for obvious reasons.