The Stratolaunch - which was founded in 2011 by Paul Allen - has an impressive wingspan of 117 metres. It has been in development for years but has just reached a top speed of 46mph on a runway in Mojave, California, and is scheduled to take the skies as early as next year.
George Bugg, aircraft program manager at Stratolaunch Systems Corporation, said: "This was another exciting milestone for our team and the program. Our crew was able to demonstrate ground directional control with nose gear steering, and our brake systems were exercised successfully on the runway. Our first low speed taxi test is a very important step toward first flight. We are all proud and excited."
The Stratolaunch has an impressive six engines and has a payload capacity of over 500,000 lbs.
They shared on their website: "Stratolaunch is the world's largest aircraft by wingspan and is the largest all-composite plane ever built. Utilising six Boeing 747 engines for a payload capacity of over 500,000 lbs. and an operational range of approximately 2,000 nautical miles, Stratolaunch is capable of delivering payloads to multiple orbits and inclinations in a single mission.
"Stratolaunch's reusability and air-launch capabilities enable us to take an airport-style approach to operations for launch services. Stratolaunch will take off from a runway, rather than a logistically vulnerable fixed range, which allows us to avoid hazards such as inclement weather, airborne traffic and heavy marine activity. Stratolaunch's airborne launch platform significantly reduces the risk of costly delays or cancellations. Stratolaunch is currently under construction at the Mojave Air & Space Port in Mojave, Calif. We aim to be fully operational by the end of this decade."