What you need for this is...
A flying mount.
Cold weather flying.
The ability to access the map of Icecrown.
Now, look at this map:
(it's a long link)
The area I filled around with the coordinate markers is the area you are going to be looking for something. (Please note that the area may or may not be 100% correct =P)
You are looking for the Alliance ship, the "Skybreaker," which is equal to the Horde's "Orgrim's Hammer." You can find it somewhere in that area I penciled in, and there will be a diagram of the Skybreaker and of the Orgrim's Hammer on your map if you are in the correct area. Take a look at this picture once you found the ship.
That's the Skybreaker. See those helicopter-type-things on the sides? That's what we're trying to get at. So, fly over to it on your mount, land on top of it, dismount, and just stand still.
Once the ship starts moving again, you will stay in the same position, not moving along with the ship. As long as you don't move your character whatsoever, you will just be standing there, up in the sky in Icecrown.
That's it.
ALSO: Sorry that I couldn't get a picture of me floating, but my laptop is in the shop, and my PC has too little RAM for WoW.