Call it “wing envy” and it seems to afflict technology billionaires. The latest example is the world’s largest airplane unveiled by Microsoft co-founder Paul Allen outside its hangar in the California desert.

Allen’s “Stratolaunch” has a wingspan of 385 feet, weighs up to 580 tons and has six jet engines. The plane is designed for airborne rocket launches, which will save jet fuel compared to launching them from the ground. The process will significantly reduce the cost of sending cargo into space.

The behemoth was rolled out of its hangar for aircraft fueling tests, according to Stratolaunch Systems. The first launch demonstration could come as early as 2019.

The plane stands 50 feet high, has 28 wheels and is expected to have a range of 2,000 nautical miles, flying at the altitude of around 35,000 feet, roughly the same as commercial planes.

The wingspan makes it the largest plane in the world, surpassing Howard Hughes’ “Spruce Goose”, the enormous wooden plane built by the eccentric mogul that made its first flight in 1947.

Allen last year wrote that having open access to low earth orbit “will deliver many benefits. For example, we could deploy more satellites that would enable better understanding of why our weather patterns are changing and help increase agricultural productivity.”

Wing envy has also afflicted Alphabet Inc (NASDAQ:GOOGL) founder Sergey Brin, who last week was reported to be building a hi-tech airship in Silicon Valley destined to be the largest aircraft in the world. Brin wants the giant airship, which he has funded personally, to be capable of delivering supplies and food on humanitarian missions to remote locations.

Meanwhile, Chinese tech billionaire Ruopeng Liu, co-founder and chairman of KuangChi Science, a Hong Kong-listed technology, has built a capsule attached to a giant helium balloon that’s capable of taking six passengers anywhere from 12 to 70 miles above Earth — an area known as near space. Liu has been dubbed the “Elon Musk of China” by local media.