REMEMBER: I do NOT code this game and I do not take any responsibility for coding anything. If you want to suggest a feature to be added to AE 4.0, contact Yuxi, NOT me.
I'm making this post to combine all the stuff that people keep saying "will be in AE 4.0!" because I (and many others) would probably repost some feature out of ignorance or just not remember every feature that apparently will come out in AE 4.0. Please reply if I need to add or remove something from this list.
-Establishment of privately owned catering and maintenance companies.
-Flights with an actual connection.
-Actual subsidiaries of an airline in Airline-Empires.
-Codeshare flights.
-Premium Economy or a "Normal" and "Premium" class for First, Business, and Coach/Economy classes.
-Cargo airlines or actual combi aircraft operations.
-Leasing spare gates to an alliance member.
-Ability to offer limited-time sales on certain routes.
-Ability to charge for certain parts of the IFE.
-Seat types, such as lie flat, angle lie flat, or recliner seats.
-Airplane crashes (that would decrease an airline's reputation).
-Leasing aircraft to other airlines/lessors, from your own airline(s).
-Charging fees for checked or even carry-on baggage.
-Alliance members could build/extend terminals in alliance hubs abroad and there would be alliance terminals and hubs.
-Reducing or increasing the number of lavatories on a plane.
-Having the option to use an airplane's airstairs at certain airports, so you would just pay for ramp fees. (Ryanair way)
-Ability to adjust the seat pitch to increase or decrease the number of seats on a certain aircraft.
-Being able to lease out gates/slots in a terminal built by your airline.
-Basing aircraft orders on aircraft type but not aircraft families.
I apologize if there's too many features that will be supposedly added, but people saying that almost about every feature will be added to AE 4.0 does mess this list up...