https://www.facebook.com/nasaarmstrong/videos/955677267825987/?fref=nf

http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-106-AFRC.html

Flight data from the first two Prandtl-D vehicles validated the
combination of twist and a lift distribution across the aircraft's wing – bell
shaped rather than the traditional elliptical shape – leads to more efficient
flight. In fact, engineers estimate future aircraft could see more than a 30
percent increase in fuel economy by using the new methods of wing design and
eliminating the weight of the modern aircraft tail and its flight control
surfaces.

In that regard, Prandtl-D research also borrows from how birds fly. Birds turn
and bank without vertical tails that are required for such maneuvers on
traditional aircraft, but not on the Prandtl aircraft.