One thing to note about airships is that the buoyancy they use to lift their cargo needs to go somewhere once they drop their cargo. You see, with a train or s

One thing to note about airships is that the buoyancy they use to lift their cargo needs to go somewhere once they drop their cargo. You see, with a train or ship, it will just exert less ground pressure or float higher in the water when you remove they payload. With an airship it will shoot straight up unless mitigated when you suddenly remove tens of tons of its weight. Unless you want to release the precious lifting gas (usually helium) you need to address this in ways that make airships quite a bit less flexible for aerial cargo transport, such as pre-arranging return cargo of similar weight or arranging for water to be taken into ballast tanks to compensate for cargo being unloaded.