Airship or dirigible is a lighter-than-air aircraft that is steerable and powered unlike free floating balloon. Airship CAD model is included. Reference: Ding-Yun Chen, Xiao-Pei Tian, Yu-Te Shen and Ming Ouhyoung, "On Visual Similarity Based 3D Model Retrieval", Computer Graphics Forum (EUROGRAPHICS'03), Vol. 22, No. 3, pp. 223-232, Sept. 2003.