Solar Impulse 2, the world's first solar-powered plane has successfully completed more than half of its round-the-world flight without fuel. The plane landed in California on Sunday after a three-day flight over the Pacific from Hawaii.

Solar Impulse 2, or Si2, was piloted by Bertrand Piccard, one of the founders of the Swiss solar aircraft. Co-founder André Borschberg said: "This flight was a huge step in the adventure and Bertrand Piccard accomplished it like a professional pilot."

"The Solar Impulse team could not have asked for a better window to complete the Pacific Crossing solar flight," he said in a statement, adding that they were teased at the start with a slight takeoff delay due to windy conditions on the runway, but the Pacific crossing followed smoothly.

Si2 took off from Hawaii's Kalaeloa Airport on 22 April during Earth Day. It was also the day when 175 nations signed the Paris Climate Agreement at the United Nations Headquarters in New York.

Piccard spoke with the UN Secretary General Ban Ki-moon live from his cockpit on the occasion. "What you are doing today in New York, signing the Paris Climate Agreement is about more than protecting the environment. It is the launch of the clean technology revolution," he said.

The Solar Impulse pilots started flying in March 2015 to continue their quest to conquer the full circumference of the earth in a solar-powered airplane - from Abu Dhabi to Abu Dhabi. They flew from Abu Dhabi to Muscat, Ahmedabad, Varanasi, Mandalay, Chongqing, Nanjing, Nagoya and Hawaii before landing at California. Si2 will next fly to New York, Europe and back to Abu Dhabi.

Si2 is the successor of the company's first airplane HB SIA, which was designed to fly without fuel and zero carbon emissions. It was unveiled in April 2014 and weighs 2.4 tons. The green technology aircraft is made of carbon fiber and is powered by four electric motors and over 17,000 in-built solar cells

The solar Impulse aircrafts can fly day and night and for longer duration. Solar cells recharge lithium batteries (weighing 633 Kg) during the day that fuels the aircraft to fly at night. The night speed of the carrier is relatively low at 40-50km per hour.