Balloon (Aviation) : An aircraft, excluding moored balloons, without mechanical means of propulsion, the support of which is derived from lighter-than-air gas
Ilan Kelman (ed.), Vulnerability and Resilience Definitions and References, Version 2, 2007. http://www.islandvulnerability.org/docs/vulnres.pd f, (Vulnr and Resilience - Brit) {524}