Dragonhawk mounts became available with Patch 3.0.8 which added the achievement, even though the dragonhawk models were already ridable as early as Patch 2.0.1 and flight masters in Quel'Thalas were given dragonhawk taxis with Patch 2.4. Three epic quality mounts are currently available to players. Of these, one is exclusively attainable by Alliance players and two for Horde aligned players.
Mountain o' Mounts
The reward for earning this achievement is a dragonhawk mount. A blue one for the Alliance and a red one for the Horde.