This is one of the reasons why the population on the forty-first floor was very small. Only those with a flight skill could make it here, and out of those, only the strongest could fly from one city to another city. The cities were very far from each other and you would have to fly for at least half a day to get from one city to another one. That means that if you start a journey from one city to another one and you just so happen to run out of mana in the middle of your trip, you would end up in a constant fall towards the non-existent ground. There was no 'ground' on this floor, so everything that is done here is either done in the cities or the air.