Airships are planned (though, admittedly we’ve seen no new info on them in years) to be a end-game creation for guilds that have battled and defeated a titan. Harvest their cores to power a players own airship to explore the planet.
I’ve not heard any confirmation of this idea being scrapped, but I’ve also seen no new info either. In my head, I assume that they’re keeping this a secret until it’s good and ready to be revealed.