Zeppelin is the first available flying unit. While not particularly lethal, it is capable of transporting two small land units, which is very useful for rapid displacement of small army groups. The main downside of the Zeppelin as a transport vehicle is that units can be loaded and unloaded only in your <l:6,104>cities<e> (to unload a unit, move the Zeppelin on a tile next to your city and then click the "Unload" button) or <l:8,24>Air Bases<e>, which makes it unsuitable for invasion. Zeppelins do not use fuel, and therefore can stay airborne indefinitely.