MIT's double-bubble design

Probably the most radical new look is the D8 "double bubble" concept from the MIT team. The group said that the 180-passenger D8 design would do the same work as the Boeing 737-800, but obviously with a wider cabin. At the rear of the aircraft are three side-by-side turbofan engines, another notable change from existing aircraft designs. Like Northrop Grumman's SELECT, the D8 would use an ultra high bypass ratio, which would mean more efficient thrust. (NASA helpfully explains: An ultra high bypass ratio means "air flow through the core of the engine is even smaller, while air flow through the duct surrounding the core is substantially larger, than in a conventional engine.")