The exact number of blimps in the world is not known with complete accuracy. Van Wagner Aerial Media, a company that offers blimp advertising services, estimates that about 20 to 25 blimps exist as of Sept. 2014. Of these, 13 are in active use.
Blimps are lighter than air vessels that have no rigid shape. A blimp only keeps its shape due the air pressure from the gas inside the structure. In most cases, the gas is helium. The main part of a blimp that does have a firm shape is the gondola. This is the cabin on the bottom of the blimp that holds the passengers.