From the article: All of these concepts rely on hydrogen as a primary power source<p>While cars are generally moving much faster towards batteries, for various reasons including that we lack a physical infrastructure to distribute and sell hydrogen, hydrogen does seem a better solution for aviation.<p>While the weight of batteries is essentially the same whether they are fully charged or not, a tank full of hydrogen gets lighter as the fuel is consumed, so it seems a much more efficient way to store energy on a transport method that it's highly subject to weight.