Paul Allen's plane – the world's biggest, with a wingspan longer than a football field – was rolled out for the first time Wednesday to start fueling and ground tests that could eventually lead to releasing rockets into space.
Billionaire Microsoft co-founder Allen's twin-fuselage Stratolaunch plane has six engines and can carry more than 500,000 pounds of payload, reported CNN.
The airplane, housed at the Mojave Air and Space Port hangar in California, is scheduled for launch demonstrations in early 2019, said Jean Floyd, Stratolaunch's chief executive officer.
"We're excited to announce that Stratolaunch aircraft has reached a major milestone in its journey toward providing convenient, reliable, and routine access to low Earth orbit," said Floyd. "… This marks the completion of the initial aircraft construction phase and the beginning of the aircraft ground and flight testing phase."
Floyd said they were working with global aerospace and defense enterprise company Orbital ATK. The Stratolaunch will be fitted to launch a single Orbital ATK Pegasus XL vehicle into space with the capability to launch up to three rockets in a single mission.
"Orbital ATK is excited by this collaboration and sees it as a positive first step in a long-term partnership," Scott Lehr, president of Orbital ATK's Flight Systems Group said last October.
"The combination of our extensive air-launch experience and the Stratolaunch aircraft has the potential to provide innovative and cost-effective options for commercial launch customers."
Floyd said current testing will "prioritize the safety of our pilots, crew and staff."
"This marks a historic step in our work to achieve Paul G. Allen's vision of normalizing access to low Earth orbit," Floyd said. "… We have a lot of exciting activity ahead as we enter the testing process, and we look forward to sharing our progress during the coming months."