The largest airplane ever to take flight has made its sophomore voyage soaring into clear skies over California's Mojave desert.

Stratolaunch's massive carrier aircraft, nicknamed 'Roc', is designed to transport hypersonic vehicles and facilitate easy access to space.

The company was founded by late billionaire and Microsoft Corp co-founder Paul Allen in 2011 and sold to private ownership in late 2019 following Allen's death.

The carbon-composite carrier aircraft has a massive 385 foot (117 meter) wingspan, and can climb to altitudes of 35,000 feet, according to Stratolaunch.

While Roc's original focus was launching satellites and eventually humans into space, Stratolaunch says for now it's priority is the in-air launch of the company's other vehicles, like Talon-A, which can reach speeds up to Mach 6.

The launch from the below the wing on the dual-fuselage aircraft means that weather related delays and other limitations of ground takeoffs can be avoided, the company says.

Stratolaunch says it is also developing a reusable space plane called 'Black Ice'.

When Allen founded Stratolaunch, it was compared to billionaire Richard Branson's Virgin Galactic - which is developing a similar high-altitude launch system - Jeff Bezos' Blue Origin and Elon Musk's SpaceX.

They all seek to cash in on growing demand for satellite launch services and, eventually, space travel, a market long dominated by industry stalwarts such as United Launch Alliance - a partnership between Boeing Co and Lockheed Martin Corp.