I love playing from the early days all of the way into the future, but with 300 airlines all operating huge planes, things get too chaotic and it just feels impossible to set up a new route after the mid-1970's. Maybe a small world with a long time scale with 5min or 10min days would be ideal to chill and would feel more realistic.
P.S. I know there are more than 300 airlines in the real world, but having 300 United/BritishAirways/AirFrance sized airlines is a bit much...