Flying has basically been an option since it was introduced in Heavensward.

In order to be able to fly, we had to run around the map, finding and touching Aether Current, but also finish certain quests with an Aether Current as a reward. Only when you've collected all of the Aether Currents, are you able to fly. In that retrospect, as long as you don't gather all of the Aether Current, you can "turn off flying" in the expansion area's (aside from Eureka and Diadem). You will automatically unlock flying in Eureka, when you clear a certain story quest in that region. The first version of Diadem had Aether Currents which you needed 3 in order to be able to fly. The recent versions of Diadem removed these, so that players could fly from the get go.

Up until 5.3 you could only walk about in the ARR area's and now (after its release in 2013) they will let us fly in these area's. However, from what i can tell, we won't have to look for Aether Currents, just finish the last quest from the 2.0 MSQ. At that point, you've already visited all of the ARR area's. (^_~ )

Correct me if i'm wrong, but i believe that the game still has ground mounts that can't fly. Why not use one of those?