Considering that a single cross-country flight puts an amount of greenhouse gases into the atmosphere roughly equal to the annual output of all of its passengers cars combined, it’s surprising that the environmental impact of plane travel is often overlooked. For that reason, I’m happy to report that there are people out there working on the problem: Robert D. Hunt in this case, with his gravity-powered plane that ostensibly can fly without the use of fuel. Further, the design of the plane grants it some of the benefits, such as VTOL and hovering capability, previously available only to zeppelins (no, the Osprey and Harrier don’t count).