Game: Sky Nations
"Sky Nations is a multiplayer sandbox game where players can join together to build air ships(cannons and all!) and do battle across a vast world procedural world full of relics and machines from another age waiting to be plundered by daring sky captains and their motley crew."
Looks like a nice amalgamation of Air Buccaneers and Minecraft. Build your own ships and bases and wage war in the skies. The game just released in alpha stage, so there's still a lot of work to be done on it, but it might be interesting to support the development here at some point.