In my world of working at an airport, this is what i see in this game that could need some tweaking to get more realistic:
Turn around times:
My record is 12 minutes to turn around a B737-800 with 186 pax inn and out. Normally i use between 20 and 25 minutes. Airlines demand using front and rear entrance during deboarding and boarding. So having 70 minutes in game to have less than 1% delay is quite off.
Game need an option to rent ground service or having their own ground service. Like, if i have 5 bases, i have My own airline ground service agents, but at destination airports, i'm renting ground service from handling agents. Kind of like the fuel providers contracts.
-For further future: implement negotiations of contracts-
Routing/Scheduling:
In Beginners world 2, i got approx 150 Aircrafts spread out on 5 bases. Average 30 Aircraft at each base. Where are they parking? There is no way any airline could have that many Aircraft parked at a stand/gate ready to depart between 06 and 09 in the morning at one airport.
At my airport, there is Airlines, that don't have a base here,but they do nightstops. I want to see this option in scheduling in the future to have an A/C to nightstop outside the base. I know it's possible to increase the turnaround time, but it just looks like the crew just had a 6 hour coffee break.