BBC: Solar Impulse is in the air again, flying the 12th stage of its circumnavigation of the globe.
The zero-fuel aeroplane left Tulsa, Oklahoma, at 04:22 local time (09:22 GMT), bound for Dayton, Ohio.
The 1,100km journey should take pilot Andre Borschberg about 18 hours to complete – a relatively short hop for the solar-powered aircraft.
But he will have to contend with steady, strong winds from the northwest as he flies northeast across the US.
Solar Impulse is aiming to get to New York in the next couple of weeks before it crosses the Atlantic – the last big leg in its global endeavour.
To complete the circumnavigation, the aeroplane needs to get to Abu Dhabi, UAE, where the flights started in March last year.
As well as setting new aviation milestones, the stated purpose of the project is to demonstrate the capability of clean technologies.
The plane gets all its energy from the sun, captured by 17,000 photovoltaic cells on its top surfaces. These power the craft’s propellers during the day but also charge batteries that the vehicle’s motors can then call on during the night.
The craft is wider than a 747 jumbo jet but weighs just 2.3 tonnes. Low flight speed means mission legs can take several days and nights of continuous flight.
The pilot is permitted only catnaps of up to 20 minutes, and the cockpit is little bigger than a public telephone box.
Journey around the world:
LEG 1: 9 March. Abu Dhabi (UAE) to Muscat (Oman) – 772km; 13 Hours 1 Minute
LEG 2: 10 March. Muscat (Oman) to Ahmedabad (India) – 1,593km; 15 Hours 20 Minutes
LEG 3: 18 March. Ahmedabad (India) to Varanasi (India) – 1,170km; 13 Hours 15 Minutes
LEG 4: 18 March. Varanasi (India) to Mandalay (Myanmar) – 1,536km; 13 Hours 29 Minutes
LEG 5: 29 March. Mandalay (Myanmar) to Chongqing (China) – 1,636km; 20 Hours 29 Minutes
LEG 6: 21 April. Chongqing (China) to Nanjing (China) – 1,384km; 17 Hours 22 Minutes
LEG 7: 30 May. Nanjing (China) to Nagoya (Japan) – 2,942km; 1 Day 20 Hours 9 Minutes
LEG 8: 28 June. Nagoya (Japan) to Kalaeloa, Hawaii (US) – 8,924km; 4 Days 21 Hours 52 Minutes
LEG 9: 21 April. Kalaeloa, Hawaii (US) to Mountain View, California (US) – 4,523km; 2 Days 17 Hours 29 Minutes
LEG 10: 2 May. Mountain View, California (US) to Phoenix, Arizona (US) – 1,199km; 15 Hours 52 Minutes
LEG 11: 12 May. Phoenix, Arizona (US) to Tulsa, Oklahoma (US) – 1,570 km; 18 Hours 10 Minutes
