World's largest airplane rolls out of hangar

The largest airplane in the world is slowly getting ready for lift-off, finally emerging from its hangar for the first time.

Eventually, the Stratolaunch plane will be used to launch small satellites into Earth's low orbit - a commercial plane reaching space.

On Wednesday (local time), the behemoth was slowly rolled out of its hangar for fuelling tests.

(Stratolaunch Systems Corporation / supplied)
(Stratolaunch Systems Corporation / supplied)

"This marks the completion of the initial aircraft construction phase and the beginning of the aircraft ground and flight testing phase," Stratolaunch Systems Corporation's chief executive Jean Floyd said.

In case the pictures don't quite capture it, the plane truly is a monster.

It has 28 wheels and a wingspan of 117 metres; the wingspan of a Boeing 737 is a mere 34 metres.

(Stratolaunch Systems Corporation / supplied)
(Stratolaunch Systems Corporation / supplied)

The next step is ground and flightline testing, Mr Floyd said.

"This is a first-of-its-kind aircraft, so we're going to be diligent throughout testing and continue to prioritize the safety of our pilots, crew and staff."

He said they're on track for a first launch demonstration as early as 2019.

"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," Mr Floyd said.