While questing in Northern Barrens there is a npc called "Wenikee boltbucket" who also offers a quest named "Wenikee boltbucket". This quest involves you talking to the npc, he will teleport you to a place, you will spawn mid-air and fall down to the ground. When landing no damage is taken and the said achievement is achieved.
I know these days this achievement is really easy with flying mount and so on, but this doesn't have the same "requirements" as other cases.