I like this idea, though you can actually extend this a further. Say, instead of selling the airport, you would pick one of your staff or hire a General Manager to replace you. Then, you take out some funds from your own coffer and start a new airport. The difference being that your starting money depends on the amount of funds you take, but over time, you will receive additional income from your previous airport. That way, the more successful airport you can consecutively manage, the easier it is to create newer airports.
EDIT: To add more merit, this could play well into the more “Corporate” side of things, essentially talking about the structure of the corporation/body/management, such as standardizing fuel supplier of multiple airports, centralizing the financing, etc.
This is eerily similar to this suggestion though.