In old Piltover, airships were a thing. You can see them in the Jinx music video amongst other things.
Since the lore overhaul however it seems like while Piltover is still an advanced society for Runeterra it isn't as advanced as it used to be. It's been pared down from a Final Fantasy VII psuedo-modern art-style society, complete with skyscrapers and modern zoos to a more Rennaissance/ Victorian Industrial era city.
Are they still there? Because you can't see them in any Piltover art depicting a skyline. I simply must know...