I will start this by saying I enjoyed the concept and simplicity Airline Empires offers. Not everyone who wants to be an online tycoon wants to worry about scheduling, maintenance checks, ensuring each snack and drink are a certain quality and what the proper seat pitch is in economy class.
The game wants you to succeed and anyone who pays attention will. I have no problem with that or anyone I competed against.
The main problem I have is it's too easy. In R5, I created an airline that in 12 years was sitting on $19 billion in cash with a healthy fleet of aircraft all company owned. Simply, the airline had reached the point where it could not fail. Even ignoring it for two days couldn't dent my profits enough to cause any worry.
I understand that this isn't supposed to be realistic and laugh when routes with demands of 1-2000 in Economy are met with the supply of 10k. As long as you know that coming in, you can have fun playing the ticket price war. I enjoyed that.
What bothered me most, however, is after you expand to where you are comfortable, there is nothing to do. You simply cannot spend your cash flow. Having planes on the go 20 hours a day makes airlines so strong, they cannot fail.
Although having a game reward you for being smart is good, there has to be some risk involved somewhere. Whether you shorten the available hours per plane or cap route supply at x amount of demand, there needs to be something involved for the player in the mid-late game stages to keep interest.