The next major replacements for the Boeing 737 and 777 models might not come from Boeing at all. MIT researchers recently presented NASA with two models for efficient, low emissions planes–part of a $2.1 million research contract awarded to the university by NASA in 2008. MIT’s objective: design quiet subsonic planes that emit 70% less NOx, burn 70% less fuel than current models, and have the ability to take off from short runways. In true MIT style, the university delivered–albeit with designs that completely reimagine the traditional aircraft silhouette.

Two models emerged from MIT’s research–The 180-passenger D “double bubble” series, intended to replace the Boeing 737, and the 350 passenger H “hybrid wing body” series, a replacement for the Boeing 777. MIT elaborates on the flying fish-like D series design:

The engineers conceived of the D series by reconfiguring the tube-and-wing structure. Instead of using a single fuselage cylinder, they used two partial cylinders placed side by side to create a wider structure whose cross-section resembles two soap bubbles joined together. They also moved the engines from the usual wing-mounted locations to the rear of the fuselage. Unlike the engines on most transport aircraft that take in the high-speed, undisturbed air flow, the D-series engines take in slower moving air that is present in the wake of the fuselage.

The D series plane travels 10% slower than a 737 to reduce drag and cut down on engine stress. But that doesn’t mean flights on the D series will necessarily take too much longer. The plane’s wide body allows for quick loading and unloading, which could make up some of the difference. And while the plane looks startlingly different from current aircraft, it is similar enough in shape to mesh with current airport infrastructure.

The triangular H series plane looks even more odd–probably because it has no tail at all. MIT explains that the massive center body generates a forward lift that eliminates the need to balance the plane with a tail, leaving us with a design that barely resembles today’s planes.

The D series and H series models aren’t MIT’s first attempts at aircraft design. The Silent Aircraft Initiative, a joint project between MIT and Cambridge University, saw the universities design a plane that is 3,000 times quieter than today’s models. Like MIT’s more recent models, the SAX-40 looks like some sort of sea creature. Which makes us wonder: Why do planes become more biomorphic as they get more efficient?