How to go from local to regional airport?

How does one go from being a local to a regional airport? And later an international airport?

It’s frustrating not seeing any rules on how to play the game. It seems a lot of information is missing and it’s not very transparent.

You can get Regional and later on, International by gathering XP from contracts. For each contract handled successfully, you get XP and SP, also an extension which extends the contract by 1 each time up to 10.

You can earn additional rewards through this such as ₩, SP, GP and even your own aircraft.

It’s the levels…
At INN you get regional and international status as follows