MMORPG.com:

It takes a special kind of environment to be able to fly, especially if there is content that you do not wish to be skipped by flying over it for example. Was this every a concern during the development?

Stephane Quilichini:

Integrating flying mounts in DnL was the biggest source of issues related to game design. Many gaming phases we originally designed had to be rewritten. We therefore made the choice to give players a higher degree of freedom by adding new functions, which are temperature and its impact on characters and pets. If you want to go beyond a mountain, you need the appropriate outfit, which is not necessarily your combat outfit. Same thing for deserts. If you fly too high, you may also see issues coming from temperature, for your mount or yourself.