Size matters - especially when it comes to launching rockets.
Initial construction on the massive airplane Microsoft co-founder Paul Allen has been quietly building in the Mojave desert, California, is complete, and the aircraft was wheeled out of its hangar for the first time on Wednesday.
Called Stratolaunch, it would be the world's largest airplane with a wingspan of 117m, or longer than a football field, and a height of 5.2m.
How big is it? It is so big that it has 28 wheels and six jet engines. It is so big that the authorities had to issue special construction permits just for the construction scaffolding. It is so big that to truly get a sense of it, you would have to see it from a distance - like a mountain.
The massive plane will not carry passengers, but rockets. Mr Allen's Stratolaunch firm has partnered Orbital ATK to "air launch" the firm's Pegasus XL, a rocket capable of delivering small satellites, weighing as much as 450kg, to orbit. The rockets would be tethered to the belly of the giant plane, and once at an altitude of 10,000m or so, the rockets would drop and "air launch" to space.