The title pretty much says it. There doesn't seem to be any difference between an aethership and the Wobbling Skies in Istan except that it's larger. According to the ambient dialogue, the pirates don't remember how they got it. It also belongs to pirates like aetherships.
An aethership looks like this: https://wiki.guildwars2.com/images/4/43/Aetherblade_air_ship.jpg