Lol, its more about economic balance. Several people posted about that already. Let me give a few insights I had while playing the game;
Not investing in baggage seems more rewarding, as investing it.
Security at baggage belts is even a gimmick without consequences atm.
Dont put money in it, until you have left over money.
The number of contracts for an airliner should be different from current (high) numbers.
As idea; put a 20 flights limit on a contract, until you can provide services for 2 star flights.
Put a 40 flights limit on a contract, until you can provide 4 star flights.
Starve contracts that are under 25% service level; have them retracted by the carrier and keep them out of the relisting queue for a year.
I would prefer a (always) challenging game on the statistic and economy side.
Yes, a lot, I have a post on this already;
In short; you cant run an economic interesting airport due to constraints in asset management (treasury management, objects, staff, vehicles, path-finding-AI, splitting operational zone reach for moving agents (staff/vehicles/planes/cars)). Multi-floor terminals and road tunnels would increase options for managing pathways a lot already.
Before you make money due to gushing profit, you can run your airport into debt forever; you should be able to go bankrupt (loose the level). Base bankruptcy on a one 1 year turnover limit; this means you have 1 year to get out of debt.
Bankruptcy could be even more interesting when you play with more economically logical loans; base them on turnover, not on start.
Anyone here remember the Bonds / Shares model in Railroad Tycoon II (still on steam), that was an awesome way to finance your business (and take risk, even bankruptcy risks)?
There are really a lot of “simple” options to make the game economically more interesting.