Roger Linfield and his colleagues at the Jet Propulsion Laboratory in Pasadena, California, who are in charge of the mission, aim to show that spacecraft flying in formation can be controlled so precisely that the distance between them varies by only a tiny fraction of a wavelength of light.

ECONOMIST: Birds of a feather

The Solar Impulse is powered by about 12, 000 photovoltaic cells that cover massive wings and charge its batteries, allowing it to fly day and night without jet fuel.

WSJ: Sun-powered plane completes California test flight