|Rocs 385 feet (117 metres) wingspan compares to 320 feet for H-4 Hercules and 225 feet for Boeing 747-8|
The aircraft, which has a wingspan of 385 feet (117 metres) and will be powered by six 747-class engines, is currently being assembled at Mojave, California.
Dubbed the Roc, the megaplane is the brainchild Microsoft co-founder Paul Allen, who is creating it under start-up firm Stratolaunch Systems.
Rare stills taken from footage shot for a recent news story by KGET 17, a Bakersfield TV station, show its huge size, according to a report by Guy Norris in Aviation Week.
The images show one of the two twin fuselage sections under assembly.
Initially, the system is intended to deliver satellites weighing up to about 13,500lbs (6,124 kg) into orbits between 112 miles and 1,243 miles (180 km and 2000 km) above Earth.
The plane will climb to 30,000 feet and launch a rocket at high altitude, avoiding the huge fuel costs of launching from Earth. -
See more photos below;
|Each of the twin fuselages of the Roc is 238 feet long and, when complete, will be supported by 12 main landing gear wheels and two nose gear wheels|