Houston, we have a big one. Engineers are now developing the largest aircraft ever flown — dubbed the "Stratolaunch" — thanks to a partnership of Microsoft co-founder Paul Allen, aerospace guru Burt Rutan, and the company SpaceX. The ambitious venture, which may cost hundreds of millions of dollars, would result in a "behemoth" carrier airplane weighing more than 1.2 million pounds, with a wingspan of more than 380 feet — longer than a football field. Its mission? To launch spaceships into orbit. (Watch a video demo below.) Here, a guide to the massive undertaking:

How would this work?
Stratolaunch would be a "reusable orbital launch vehicle," says Rebecca Boyle at Popular Science, and a "potential replacement for the space shuttle." The "massive parallel-fuselage carrier airplane" would take off on a 12,000-foot runway and haul a Falcon 9 rocket into the stratosphere. Once high enough, the rocket would be let loose, and then launch into orbit.

How will they build it?
The "super-carrier" would require six 747 engines, and the team already has a contract to acquire two planes from Boeing. The super-plane's metal skin would be built from "advanced carbon composites," says Alan Boyle at MSNBC. The Stratolaunch is expected to take flight within five years.

Why is this such a big deal?
This could "make spaceflight routine by removing many of the constraints associated with ground-launched rockets," says former NASA Administrator Michael Griffin, who now sits on Stratolaunch's board of directors. Plus, says Jason Paur at Wired, using the plane gives space missions more versatility, since rockets could be launched from any airport equipped with a long runway. Once finished, Stratolaunch "will begin by launching cargo into orbit," says Paur. The company would only begin selling tickets to humans "once the technology is proven."

Check it out:

Sources: MSNBC, Popular Science, Wired