Why Microsoft cofounder Paul Allen is building an airplane as wide as a football field

The "Stratolaunch," the world's largest airplane, is 76 percent complete.

Created by Microsoft co-founder and Seattle Seahawks owner Paul Allen, the Stratolaunch will be larger than any other airplane every built. According to Christian Davenport at The Washington Post, the plane is staggeringly huge:

• Its wingspan measures more than the length of a football field - 385 feet
• The landing gear contains 28 wheels
• Once loaded, it'll weigh 1.3 million pounds
• It contains 60 miles of wiring
• It's powered by six 737 engines

Originally announced by Allen in 2011, the plane has "beyond-Earth ambitions": it's designed to carry a rocket to 35,000 feet. At that height, the rocket (which is tethered to the plane) will "air-launch" into orbit.

"When such access to space is routine, innovation will accelerate in ways beyond what we can currently imagine," Allen said in a statement to the Post. "That's the thing about new platforms: when they become easily available, convenient and affordable, they attract and enable other visionaries and entrepreneurs to realize more new concepts."

So far, no set date for the plane's first flight has been revealed - and, according to the Post, the plane still needs to go through a ground-testing program - but Allen's Vulcan Aerospace is on track to launch rockets by the end of the decade.