Microsoft co-founder Paul Allen today is announcing plans to build the world's largest aircraft to start a new orbital cargo business, joining the ranks of billionaire investors blending their love of space and science fiction with the growing opportunity for private space ventures.

For Allen, the venture combines his lifelong interest in science fiction and technology with his entrepreneurial streak. The name of the company also hints at his love for rock music and guitars, such as the classic Stratocaster.

Building the largest aircraft of his generation will also draw comparisons to another mysterious tycoon - Howard Hughes, who spent heavily to build the world's largest flying boat in pursuit of a cargo business that never materialized. The Spruce Goose flew once, in 1947, and is now displayed in Oregon.

Allen's working with aircraft designer Bert Rutan, with whom Allen developed SpaceShipOne, the first privately built spacecraft to enter sub-orbital space in 2004.

For the new company, Stratolaunch Systems, Rutan (at left, with Allen) is building a giant cargo plane powered by six 747 engines and with a wingspan over 380 feet. It will be constructed in California at the Mojave Air and Space Port.

Work has already begun on the craft and it should be operating within a decade, Allen said at a press conference in his office near the Seahawks stadium south of downtown Seattle.

Allen said as a boy he built model rockets and he and his mother watched for the first astronaut's flight. Now he hopes to build something today's children will look for in the sky.

The craft will require a huge runway - 12,000 feet long - and will operate from a spaceport such as Kennedy Space Center.

Allen's team includes former NASA leaders and partner companies including aerospace engineering company Dynetics and PayPal veteran Elon Musk's Space Exploration Technologies, which will build a multi-stage booster for the aircraft.

The company hopes to fly people into low earth orbit eventually but it's going to start by delivering unmanned payloads.

A rendering of Allen's planned craft: