Abstract: A modular unit 129 for forming an airship 100 includes an elongate spine 106 intended to extend along a longitudinal axis of the airship 100. The spine 106 includes a number of interconnecting elements 108 each of which has connection means 182 for being joined in end to end relationship with an interconnecting element 108 of an adjacent modular unit 129. Buoyant support means in the form of gas bags 105 are fixed relative to the spine and are positioned within annular spaces 132 and 134. The invention also extends to an airship 100 which may be formed from a number of modular units 129 connected end to end and with a central spine 106 extending between outer extremities 116 and 118. A gondola 101 is located within a lower half of annular space 102 such that an outwardly facing surface is flush with an outer surface of the airship 100.