Rin, I'm insulted you didn't think there'd be sky pirates.

I'm kind of imagining that there's... maybe a giant storm, or series of big storms, that contain certain clusters of islands. Within those clusters, people can get around on flying mounts like birds or bats, but travel between them needs an airship. Maybe different clusters use different animals? I'm imagining the sky-pirates giving their mounts little goggles and bandannas, maybe painting a Jolly Roger on them if space permits.