Worldofwar.net reports that Blizzard community manager Nethaera has spoken about the possibility of allowing flying mounts in WoW's early content.
Apparently, it's just a technical problem, rather than a decision by Blizzard that is stopping this being possible right now.
"As you can see by the recent mount changes, this could be readdressed at a future point in time...
...We're always taking a look at different aspects of the game and trying to find a way to improve upon the experiences that players get to have within it."
