Stratolaunch Systems said it has moved its massive Roc aircraft out of its hangar for the first time on Wednesday in preparation for fueling tests, and eventually ground and flight testing.

The company is building the first-of-its-kind airplane, called Roc, at the Mojave Air & Space Port in Antelope Valley to launch satellite-carrying rockets into orbit. Northrop Grumman Corp. subsidiary, Scaled Composites, is building the craft. When completed, Roc will be the largest aircraft in the world with a wingspan of 385 feet – longer than a football field.

Stratolaunch Chief Executive Jean Floyd wrote in a posting on the company’s website that over the past few weeks, the three-story scaffolding around the aircraft had been removed, enabling the craft to rest its full weight on its 28 wheels for the first time.

“This was a crucial step in preparing the aircraft for ground testing, engine runs, taxi tests, and ultimately first flight,” Floyd wrote.

The Stratolaunch flight system uses the Roc to take a rocket to high altitude and release it so the rocket can fly into space. Stratolaunch was founded in 2011 by billionaire Paul Allen to launch satellite-carrying rockets into orbit as a lower cost, more convenient alternative to ground-launched rockets.

The Roc’s first launch demonstration could come as early as 2019.