Solar Impulse lands in St Louis in trans-America bid

The HB-SIA Solar Impulse plane approaches the St Louis runway

A solar-powered plane aiming to cross the US from the West Coast to the East Coast has completed its third leg.

The Solar Impulse vehicle made the journey from Dallas to St Louis in 21 hours, 22 minutes.

The HB-SIA craft, which has the same wingspan as an Airbus A340 but weighs just 1.6t, landed at Lambert-St Louis International Airport at 01:28 in the morning local time (06:28 GMT).

The fourth leg will run to Washington DC in the next few weeks.

The pilot duties on the "Across America" bid are being shared by the two leaders of the project - Swiss nationals Bertrand Piccard and Andre Borschberg. The Dallas-St Louis segment was undertaken with Mr Piccard at the controls, and it represented his longest flight in the vehicle.

For much of the third leg, the solar aircraft flew below cirrus clouds, but continued to charge its batteries.

The flight distance of 1,040km (560 nautical miles) from Dallas to St Louis was completed at an average speed of 49 km/h (26 knots).

The Solar Impulse team has had to erect a temporary hangar at St Louis to house the plane. Recent storms damaged the building that was originally assigned the task. An inflatable hangar is going to be used to park the aircraft while it is in the city.

The trans-US journey is billed as the first cross-continental, solar-powered flight by a craft capable of flying in hours of daylight and darkness.

It is the last showpiece with the prototype aircraft before Mr Piccard and Mr Borschberg attempt a trans-oceanic flight and an eventual around-the-world flight in 2015.

The aeroplane already holds records for the first international flight of a manned solar-powered plane in 2011, and first inter-continental flight in 2012.

The aircraft completed the first leg of its trans-American bid - between San Francisco and Phoenix - in early May, in a flight lasting 18 hours. The second leg - from Phoenix to Dallas - was completed in late May. This trip covered a distance of 1,541km (958mi) - a record for a manned solar-powered plane.

The Across America project coincides with the Piccard's and Borschberg's Clean Generation Initiative, an effort to encourage policy-makers and businesses to develop and adopt sustainable energy technologies.