'World's largest plane' makes its first flight

An aircraft dubbed the world's largest aeroplane has taken off over the Mojave Desert in California on Sunday, in another step towards the manufacturer's bid to enter the lucrative private space market.

Built by Stratolaunch Systems Corp, started by late Microsoft co-founder Paul Allen, it was the first flight for the carbon-composite plane.

Called Roc, it has a wingspan the length of a football field and is powered by six engines on a twin fuselage.

It stayed aloft for more than two hours before landing safely back at the Mojave Air and Space Port as a crowd of hundreds of people cheered.

"What a fantastic first flight," Stratolaunch chief executive officer Jean Floyd said. "We are incredibly proud."

The flight furthers the manufacturer's mission to provide a flexible alternative to ground launched systems.

The plane is designed to drop rockets and other space vehicles weighing up to 226 tonnes at an altitude of more than 10,000 metres, and has been billed by the company as making satellite deployment as "easy as booking an airline flight," Floyd said.

Allen, who co-founded Microsoft with Bill Gates in 1975, announced in 2011 that he had formed the privately funded Stratolaunch.

The company seeks to cash in on higher demand in coming years for vessels that can put satellites in orbit, competing in the United States with other space entrepreneurs and industry stalwarts such as Elon Musk's SpaceX and United Launch Alliance - a partnership between Boeing and Lockheed Martin.

Stratolaunch has said that it intends to launch its first rockets from the Roc in 2020 at the earliest.

Allen died in October 2018 while suffering from non-Hodgkins' lymphoma, just months after the plane's development was unveiled.

"The aircraft is a remarkable engineering achievement and we congratulate everyone involved," said Jody Allen, Chair of Vulcan Inc and Trustee of the Paul G Allen Trust.

"We all know Paul would have been proud to witness today's historic achievement."