The Swiss plane Solar Impulse has left on the first leg of its journey across America that will take it in five stages to New York. It is expected to end the trip in about two months time.

Piloted by Bertrand Piccard, the aircraft left Moffett Field in Mountain View near San Francisco early on Friday local time for a flight to Phoenix, Arizona, expected to take 15 to 20 hours.

Solar Impulse, which relies for its power solely on the sun, consumes about the same amount of energy as a motor scooter. The power comes from 12,000 solar cells built into its wings, which simultaneously recharge batteries with a storage capacity equivalent to those of a large electric car. This is how it can continue to fly after dark on solar energy generated during daylight hours.

It can climb to 8,500 metres and flies at an average speed of just 69 kilometres per hour.

It is the first solar-powered aircraft capable of operating day and night without fuel to attempt a US coast-to-coast flight. After each stage it will remain on the ground for several days to enable the public to see it.

Solar Impulse, which has the wingspan of a jumbo jet and weighs about the same as a small car, is a test model for a more advanced aircraft the team plans to build to fly round the world in 2015.

In compliance with the JTI standards

More: SWI swissinfo.ch certified by the Journalism Trust Initiative