I'm sure this has been asked and answered many times, but why is it designed this way? Obviously real world airlines make profits with large long haul.
Its not that we specifically sat down and make it work like this, it is more the dyanmics of the game and the model we use. There is no connecting traffic in AM, and there is only a small bonus at airports for large networks. The entire game is built off of single class of service, at maximum economy configuration for seating. The best financial results are from medium sized narrow body aircraft where a strong fare can be maintained with a low frequency. When you try to benchmark a long-haul route in AM vs the real world you will find only a few examples where these are similar.
The assumptions and the model are far from perfect but so far they have delivered an easy to use game that many people enjoy. We are always working on improvements, and model improvements are a little bigger and are less likely to appear in any game world without a major change.