Two parts: Propellers for the engines already in the game A mast with a big ecliptic balloon to provide lift which attaches to the two ship hulls much like the regular masts. Perhabs fueled like the steam engines before its able to fly and with a high consumption to balance the advantage of being able to fly between islands. That way we can lose our ships in an even more spectacular fashion ? I have no idea how hard it would be to implement, but it would fit...

Well I still can't figure out how to edit an exploration game with the editor.. When I open the savegame with the editor it makes a new "editor" save which I can't figure out how to load as an exploration game afterwards.. I'm probably doing something wrong ? The good news is that when I opened the savegame to move my ship back to the spawn island (the editor opens at my spawn island) all the stuff was back on the ship.. So perhaps the problem...

Gamemode: singleplayer, exploration. The ship was all ready fitted with some containers and other free placed blocks, as well as some on grid, when I loaded my save file. So then I placed all sorts of things on my ship. Wooden boxes (on grid), sacks (free placed), barrels (free placed) and some decorations (bear trophy, some books and candles, a seashell jar (with inventory) and a pigment jar (empty). I then sailed around a bit enjoying this...