@Pasi Thank you for your insight
@Blokker You may be right, but I probably have forgotten the most important element. Regardless whether fares are calculated based on either euclidean distance or transported distance (if someone has some information on that please tell me), then it is better to have straight lines to transport passengers farther. If I have cities A,B,C with 10 km distance between each, in a circular line I only transport passengers for 10 km regardless where they want to go, If I have cities A-10km-B-10km-C passengers wanting to go from A-C or C-A travel 20km. On average (including A-B and B-C 10 km) that makes 15 km. That should earn on average 50% more revenue. Maybe circular lines are able to reduce travel time and are able to attract more passengers, but I’m not sure it will compensate the loss on revenue. Am I missing something ?
Note: if fares are calculated by euclidean distance (as I suspect but am not sure) then the position of the cities need also to be different… on a straight line as opposed as on a circle.