I would love to see this mod made for Bukkit! My husband has it on his singleplayer world, and I would love to have this on my server. http://www.minecraftforum.net/viewtopic.php?f=1032&t=178612&hilit=steampunk+airship Nothing like a hot air balloon ride!
Er... im kinda sorry to say this, but custom vehicles won't be possible in multiplayer, without modifying the client! The closest you can get is probably movecraft, which is currently broken at the time of writing. But that would've been so cool!
Aww, wish it worked! I use Skypirates for flying atm, but I have a nasty habit of clicking myself out of the boat to my death. What I really need is the function that the Airship has for up and down.. using e for up and c for down.. less... splatting that way.
I would prefer the Airship. a flying boat is kind of like magic carpet, so I could do with-ought it. I would really like some usable planes and airships for an airport I am building, but the airships would look better.
The creator for the Planes mod is planning to implement SMP compatibility at some point: http://www.minecraftforum.net/viewtopic.php?f=1032&t=198188
You can do this with MoveCraft, it is fixed now, although the movement won't be as smooth as with a client mod. I don't know alternatives for SMP atm. MoveCraft