I find that a big reason a lot of in-game realistic airlines go bankrupt is because when they are small airlines, they don't route planes when they get them, or a few hours after, but instead wait for a day and do it for some reason.
+1
You have to have good dedication. Preferably checking AE at least twice on a daily basis. Running profitable and realistic airlines takes a lot of work, dedication and practice. That's why it took me 3 years to work it out. But it is well worth the investment if you are after the level of respect a community will give you. I used to get harassed in the community so much, but that doesn't happen anymore. I am proud of how far I personally have come, and many people on here have the potential to do at least as much. Beating spammers just requires a certain knack for demand manipulation