Eloderung from the World of Warcraft Forums took a couple of videos from the Public Test Realm that might just interest you: Engineering mounts. The said mounts can be built by engineers - an addition brought about by the upcoming WoW patch 2.3 from Blizzard.

The player even posted some notes on the flying contraptions:

• Mountspecial does nothing unusual.
• The mount randomly shoots up in the air during as part of its ground idle animation.
• The bobblehead doll on the dashboard dances and bobs its head in flight :D
• Lots of moving parts. Particle effects from the back of the jets. Blue jet flames while in flight. Youtube quality doesn't do this mount any justice - this is quite impressive, visually.