This page explains how to find Fly (TM94) - a Flying-type HM Move (Hidden Move) that allows you to fly between previously visited towns in Pokemon Brilliant Diamond and Shining Pearl (BDSP).
Fly - Move Details
|Flying||Physical||90||95||15||The user flies up into the sky and then strikes its target on the next turn. You can also travel between cities with it.||TM94|
Fly HM Location
HM Fly allows you to fly between cities you’ve already visited - like fast travelling!
After you’ve defeated Gym Leader Maylene to earn the Cobble Badge, you will find a Tm94 ball to the right as you first enter Team Galactic Warehouse in Veilstone City. It’s worth noting that you could pick up the TM94 ball prior to defeating Maylene, and so if this is the case, you won’t have access to the HM until you’ve beaten Maylene.
How to Use Fly
Using fly is easy, all you have to do is open up your map and hover over a city you’ve been to previously and press A to have the option to travel there by flying.