The Flying-V

The Flying-V was designed as a fuel-efficient, long-range aircraft in which the passenger seating, fuel tanks and baggage hold are built into the wings. Research shows that the unusual design stands to gain up to 20 percent better fuel efficiency than an Airbus A350 jetliner, considered today’s most advanced design. It’s also about 15 percent more aerodynamically efficient than conventional aircraft. At full scale, the Flying-V would seat 314 passengers in two classes... More here.

That is an incredible design.