I think it is kind of unrealistic with the way that the terminals work. Firstly the airports don't have the correct number of gates, but this isn't a huge problem. What, in my opinion, is, is the second reason; that all the airports have infinite capacity it would appear if an operator has a little bit of money. To add 66 gates to Heathrow with the construction of Terminal 5 cost £4.2 Billion (€5.3 Billion) The current cost to add a similar amount of gates is nowhere near that. So 2 suggestions I would make are as follows:
1) Each airport has a fund that any airline can add to and when it gets to certain points construction begins on a new terminal and this takes a period of time upwards of 1.5 years. The gates from this construction are then available to everyone to rent.
2) When you want to own gates without paying the rent fee, currently by building a terminal, you by the gate from the airport instead. If you have added to the fund to build the new gates mentioned in point 1 then aslong as some of the gate remain to buy then you can get them at a reduced rate.
A third point that would not need to be made but might benefit the game is:
3) Gates have a time limit at them which is used by the turn around + 30mins per aircraft. e.g. a gate might have 20 hours and you have a plane with turnaround time of 0.5 hours add onto this the 0.5 hours extra then you can land that plane 20 times for that gate. (Needs work)
