A solar energy plane has landed in Morocco, completing the world's first intercontinental flight powered by the sun to show the potential for pollution-free air travel.

The Solar Impulse took off from Madrid on Tuesday and landed at Rabat's International airport after a 19-hour flight. Shortly before Swiss pilot Bertrand Piccard landed in Rabat, the project co-founder and pilot Andre Borschberg said the aircraft had proved its sustainability.

"It can now fly day and night. It's quite a show ... a technology we can trust," he told reporters.

Pilot Piccard descended from the plane, smiling as he was greeted by Borshberg and Mustafa Bakkoury, the head of Morocco's solar energy agency.

The Solar Impulse project began in 2003 with a 10-year budget of à90-million and has involved engineers from Swiss lift-maker Schindler and research aid from Belgian chemicals group Solvay.

On Tuesday, the aircraft crossed the Gibraltar Strait, separating Africa and Europe at one of its narrowest points. The flight is crucial for the project's developers because it would help improve the organisation of a world tour planned next year.