"no illusions that solar-powered flight will soon be an option for mass travel"

Solar-powered plane flying across US lands in Washington DC | Suzanne Goldenberg - Environment | The Guardian

By the time the Solar Impulse touches down in New York, the trip from San Francisco, via Phoenix, Dallas, St Louis, Cincinnati, and Washington, will have taken nearly two months. The team could have driven that distance by car several times over. But speed was not the point, said Piccard.
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On calm, clear days, the plane climbs up to a maximum altitude of 28,000ft (8,500 metres), and then enters into a slow, gliding descent, switching off the engines to save power.
It's a process that is repeated multiple times during the course of the long flights, turning a ride in the Solar Impulse into something like a slow-moving airborne rollercoaster.
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As the pilots have learned, huge wingspan and light weight are a terrible combination during turbulence, and for the violent storms that are a part of an American spring.
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In Dallas, the headwinds were so strong the Solar Impulse, chugging along at 40mph or so, was travelling backwards for a time, before Borschberg, whose turn it was at the controls, could correct course. "The wind speed was the same as the maximum speed of the airplane, which means I could position the airplane above the airport and the airplane was not moving," he said.
..."There are some quite strong crosswinds coming from the left, so we have to correct and fly a little bit sideways," Piccard said. He also dropped to below 4,000 metres. "Above that the wind might push me to Florida – not to Washington DC," he said.
But by the time the plane touched down in Washington DC, those tense moments were behind Piccard. He and Borschberg were looking ahead: to the final leg of this journey, and their next one: a trip around the world by solar plane in 2015.
The two men are under no illusions that solar-powered flight will soon be an option for mass travel, however.

Balloon (aircraft) - Wikipedia, the free encyclopedia

On 1 March 1999 Bertrand Piccard and Brian Jones set off in the balloon Breitling Orbiter 3 from Château d'Oex in Switzerland on the first non-stop balloon circumnavigation around the globe. They landed in Egypt after a 40,814 km (25,361 mi) flight lasting 19 days, 21 hours and 55 minutes.