The Stratolaunch aircraft is designed to launch satellites and eventually passengers into space. The plane has two fuselages, 28 wheels, six engines and a wingspan almost double that of an Airbus A380.
The world's largest aircraft successfully completed its first test flight on Saturday.
The massive plane with a wingspan larger than a football field took off from an airfield in California's Mojave Desert and conducted testing exercises for 2.5 hours, according to Stratolaunch Systems, the space transportation company behind the project.
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During the flight, the Stratolaunch aircraft reached a maximum speed of 189 miles per hour (304 kilometers) and altitude of 17,000 feet (5,182 meters).
The aircraft with a wing span of 117 meters weighs 220 tons, has two connected fuselages and 28 wheels, and is powered by six Boeing 747 engines.
Stratolaunch is designed to be a mobile platform for launching satellites into space. It may one day also launch passenger shuttles into space.
"Today's flight furthers our mission to provide a flexible alternative to ground launched systems," Stratolaunch CEO Jean Floyd said.
The project was developed by Microsoft co-founder Paul Allen, who died last October.
"We all know Paul would have been proud to witness today's historic achievement," said Jody Allen, chair of Vulcan Inc. and trustee of the Paul G. Allen Trust. "The aircraft is a remarkable engineering achievement and we congratulate everyone involved."