I've created this topic to add from time to time my suggestions for AE evolution and avoid digging out some older topics.
For now they are:
1) Reducing the number of airports to their real quantity in a time (e.g. in 50's or 70's of XX century) - but this has been mentioned before...
2) What about a stock market? Airlines could trade their or others' shares to make additional profits...
3) Differentiate the cost of marketing categories. Now - however there is an info that one is more costly than other - their cost is exactly the same and depends only on percent of sales we want to spend on them.
4) Let's make fuel buying non-automatic - there could be a fuel market with fluctuating prices and everyone would have to make additional decisions whether to buy and if so - how many?