Okay here are my comments/suggestions.
After you register an account you should be redirected to the login page with the message saying "Your account has been created", instead of showing the register page again, preferably you should automatically log the person in after they have registered.
After having a test of the game I can say that the main thing that I don't like about it is the sidebar menu, the black text on a brownish grey background is far too difficult to see. Maybe you could make the text bigger, bolder and lighter to make it stand out more. Also you should try to reduce the number of links in the sidebar, you could possibly spilt the links into sections somehow (by making the red sections colapsable and expandable), just so that there aren't so many actions to scroll through.
Important things such as actions (eg. search, market, airport and etc.) could be place in a separate place to make them clearer, a good place would be under the logout/refresh buttons.
The game actually looks quite detailed so that is good!
