A solar-powered plane made a third successful test flight in the United Arab Emirates on Monday ahead of a planned round-the-world tour to promote alternative energy.
Organisers hope that Solar Impulse 2 may head off around the globe as early as Saturday but caution that the launch is dependent on the weather, even in the relatively cloudless Gulf.
The hour-long test flight was the plane's third from the UAE capital Abu Dhabi's small Al-Bateen airport, but the first for Solar Impulse chairman Bertrand Piccard, the descendant of a family of Swiss scientist-adventurers.
The pilot reported no problems, mission chiefs said.
The project is the fruit of 13 years of research and testing by Piccard and Andre Borschberg, two Swiss pilots whose idea was initially ridiculed by the aviation industry.
Their plane is powered by more than 17,000 solar cells built into its wings which, at 72 metres (236 feet), are almost as long as those of an Airbus A380 superjumbo.
The light-weight carbon fibre aircraft weighs only 2.3-tonnes, about the same as a family 4X4 or less than one percent of the weight of the A380.
The two Swiss pilots aim to demonstrate that "clean technology and renewable energy can achieve the impossible," Piccard said.
It will then head on to Myanmar, China, Hawaii and New York.
Landings are also earmarked for the midwestern United States and either southern Europe or north Africa, depending on weather conditions.
The plane is the successor to Solar Impulse, a smaller craft which notched up a 26-hour flight in 2010, proving its ability to store enough power in lithium batteries during the day to keep flying at night.
The new plane will travel at speeds of between 50 and 100 kilometres per hour (30 and 60 miles per hour), the slower speeds at night to prevent the batteries from draining too quickly.
The pilot will be linked to a control centre in Monaco and the aircraft is scheduled to arrive back in Abu Dhabi in July.