So I've been developing a world with a 19th century gaslight aesthetic in which airships are commonplace, as are seaships. And to add to this there are also rudimentary Red Baron style fighter biplanes. All three of these are used in a military capacity. My question is how to categorise airships. Seaships are obviously part of a navy, with fleets, armadas etc. And planes are obviously part of an airforce, with squadrons and stuff. But where do airships fit into this? You could say they're a navy because, well, airships. But they are in the air, so airforce would also make sense. And then there's the problem about, whichever of the two airships fall into, how do you distinguish them from the seaships and planes that also fall under that category?