Hybrid Airships attempt to combine aerostatic lift, from the conventional Lighter Than Air (LTA) concept, with various Aerodynamic lift capabilities derived from the heavier-than-air industry. Hybrid airships have been proposed for many years, and there are a variety of projects that have attempted to marry the technologies together.
Lockheed Martin were the first organisation to fly a manned proof of concept vehicle with their P791, which first flew in January 2006. Although video of the first flight shows, what appears to be, alarming instability, Lockheed Martin stated in late 2011 that they have resolved any stability issues using avionics software.
Hybrid AIr Vehicles were sub-contracted by Northrop Grumman to build a vehicle for the US Army under very tight time constraints. The Long Endurance Multi-intelligence Vehicle made its maiden flight on 7 Aug 2012. Plans to develop a heavy lift transport varient, now rebranded the Airlander, are on-going.
The Boeing Skyhook project apparently progressed to design freeze, but there were insufficient backers to take the project to the prototype stage, and it was subsequently shelved.
In addition to aerodynamic lift, there is also the potential, initially proposed by Jean-Francois de Roziere, of heating the lifting gas to increase available lift. The principle has been used in the Ballooning world for several world records, but has not yet (to our knowledge) been successfully applied to a Helium airship. There is currently a renewed interest in the Hybrid concept, both for heavy lift and for surveillance purposes from the US Military.