Watch Microsoft Co-Founder Paul Allen’s Giant Stratolaunch Plane Taxiing on the Runway
The enormous Stratolaunch aircraft, created by Microsoft co-founder Paul Allen, isn’t quite ready to fly. But he has taken the super-sized plane out on the runway for a test ride.
Allen shared new footage of the Stratrolaunch taxiing on the runway over the weekend in Mojave, Calif.
The Stratolaunch is a gigantic aircraft that resembles two airplanes glued together by a single wing. The goal is to create a large airplane that can more easily fly to Earth’s low orbit than conventional spacecraft, and do things like launch satellites.
Allen said on Twitter that the Stratolaunch zoomed to speeds of 46 miles per hour on Sunday, which exceeded the speed it hit during a runway test in December, when it reached 28 mph.
Although rolling along airport runways is not noteworthy for typical airplanes, the Stratolaunch is no typical airliner. If it ever gets airborne, the Stratolaunch would be the largest airplane to ever fly.
Get Data Sheet, Fortune’s technology newsletter.
As tech publication Ars Technica notes, the Stratolaunch’s wingspan of 117 meters, or 385 feet, is longer than that of the World War II era Hughes H-4 Spruce Goose, which had a wingspan of 97.5 meters, or 320 feet.