Couple suggestions

Had some ideas im pretty sure havent been posted yet, and may not be too hard to implement.

1. Choose airline route map colours - Instead of just standard blue, allow to match the airline. Ie Qantas could have a red map

2. Airline Partnerships - Code-sharing would probably be too complex, but to make an agreement to not compete on any more routes, and then see an increase in sales for both airlines from recommended transfers might be an idea.

3. 747-400ER - Same capacity as the actual 747-400, but allowing it to fly Sydney Dallas direct, which can't be done at the moment

4. Refilling hubs - This has had a mention, but to connect the three places, even if it is listed as two routes (ie Sydney-Singapore next to Sydney-London via Singapore

5. Higher number of total airlines, but significant variation in airline size. Regional centers and carriers may also be an option, deliberately only using smaller aircraft, but only visiting cities with little demand

6. Government regulations on some routes:
a) Limited landing slots
b) Have to be matched by local competitor
c) Limited number of seats per aircraft that lands to simulate aircraft size
d) Maximum number of carriers on a certain route / there has to already be an AI competitor on that route

7. Ability to set up separate regional / independent / budget airline and manage it in a separate manner

8. Christchurch! And accurate Melbourne population

9. Purchasable in-flight upgrades to increase appeal over competitors (entertainment systems and such)

10. An indicator of how much of a route is not serviced (Also previously mentioned)
a)Increases in numbers from hub routes (Again... mentioned)