So as routes between large cities get taken, you need options to expand your airline without competition (if you are new). I found out you can make good money (7000-9000 K) with a route opening strategy:

1. Find a decent size city with ratings at about 200 for both business and tourism, with little competition.

2. Get a plane similar in size to these examples: DC 10, MD 11, A330, 777

3. Make routes to huge cities (London, Los Angeles, Rome, Athens, Houston, etc)

You are now ready for easy, free competition money making.

If you think that this strategy is wrong, feel free to correct me. In my defense, this is the first time I am playing this game somewhat seriously. By the way, I am on ATO2