Inside the world's largest plane, which has a wingspan longer than a football field and will debut in 2019

• The Stratolaunch is the world's largest aircraft.
• Its 385-foot wingspan is longer than a football field.
• The aircraft recently completed a runway test in anticipation of its debut flight, which is planned for 2019.

The world's largest plane is so big, it needs two fuselages with separate cockpits.

It's called the Stratolaunch, and it's designed to launch rockets into space in what is known as low-Earth orbit, which means the spacecraft is between 99 and 1,200 miles above the Earth's surface. (Most space flights, as well as satellites and the International Space Station, are in low-Earth orbit.)

Since it was unveiled in June 2017, the Stratolaunch has undergone a series of tests before it makes its first flight in 2019. On Monday, the Stratolaunch YouTube page posted a video of runway tests that saw the aircraft reach a top speed of 46 mph.

Here's a look at the Stratolaunch, and why businesses might want to use it.

SEE ALSO: Trump strikes $3.9 billion deal for two presidential Boeing 747s — here's a look back at the incredible history of Air Force One

Stratolaunch Systems is owned by Paul Allen, who cofounded Microsoft.

Allen's goal for the company and its namesake aircraft is to "provide convenient, reliable, and routine access to low-Earth orbit."

It would do so by launching rockets toward space from mid-air, which the company hopes will be less expensive than current, commercial space launch options.