I started playing 3 games at the same time, and I had to stop the other two and focus on the Euro Challenge with Lakeland Airlines just because it provides the most challenge. I will have to agree with Chrissy on making the route planning a bit smarter, meaning sorting airports by availability as well, and perhaps it would be a good idea to also know how many first class or business class seats are available.
What was a bit frustrating was that in the beginning of the game I joined at a relatively early stage of the game, about 2-3% and I found it a bit difficult to catch up. Perhaps you could have an adequate notification of a new game a couple of weeks in advance, either by messages on the participant's inbox, or an email to our personal addresses that you use for registration.
In any case, feedback is the food of champions, and this is a great game, but of course, telling you how good it is won't make it any better. I have a couple of suggestions for the overall game though, which you may wish to consider.
1. You listed the airport of Ercan in North Cyprus as a European airport. As you may very well know, the TRNC is an illegally formed state that is only recognized by Turkey, not by EU or the UN. You even have the flag of the TRNC, which is extremely offensive to people from Cyprus and Greece. Please consider removing that airport from the map. In any case, in real life, the only commercial and chartered flights flying there are from Turkey, so for this game at least it is useless.
2. The route Athens to Larnaca, is perhaps one of the busiest routes in Eastern Meditterranean. The demand in this game, is approximatelly 80 people, but there are at least 10-12 flights daily from Larnaca. Perhaps you can improve that in the future.
Thanks again for creating this game, and keep up the good work