On a summer afternoon high above the Swiss Alps, Raphaël Domjan stared out at a commercial airliner flying below him.
At 9,500 meters (31,000 feet), Domjan was alone in a featherlight aircraft powered not by jet fuel, but exclusively by the sun.
For more than five hours on August 12, the Swiss explorer climbed and coasted through the thin air in SolarStratos, a solar-electric plane no heavier than a grand piano, breaking the world altitude record for its class—pending official confirmation. The aircraft, called HB-SXA, is part of a bold attempt to prove that solar-powered flight is not only possible but ready to rival some conventional aircraft at high altitudes.
“Up there, facing the sun that powers our wings, flying without burning a single drop of fuel is an indescribable feeling…a moment out of time,” Domjan later wrote.
A New Ceiling for Solar Flight
Domjan’s flight took off from Sion Airport in western Switzerland and climbed steadily for over two hours. Flying alone, and dressed in a pressure suit more often seen on astronauts than aviators, he reached 9,521 meters—just over 31,200 feet. It’s the highest a manned solar-electric aircraft has ever flown, beating the previous record of 9,235 meters set in 2010 by Solar Impulse pilot André Borschberg.
At cruising height, Domjan’s aircraft briefly crossed paths with a commercial jetliner—one burning tons of fuel, the other floating on solar power and alpine thermals. The contrast was poetic, but the symbolism was hard to miss.
“[It was] a moment of great pride and emotion for the entire SolarStratos team—fittingly celebrated with a well-deserved raclette!” the project team announced after the flight.
Though the record awaits verification by the Fédération Aéronautique Internationale, Domjan is already looking ahead. “The mythical 10,000-meter mark is within reach,” he said, as per Flying. “Next goal: touch the stars with nothing but the power of the sun.”
The Future Is Ultra-Light and Ultra-Clean
HB-SXA, the aircraft that carried Domjan to new heights, was never meant to compete with jumbo jets. Built by Germany’s Elektra Solar and modified by the SolarStratos team, it weighs just 450 kilograms (992 pounds) and has the long, slender wings of a glider. These 25-meter wings are clad in solar cells covering more than 22.4 square meters—enough to keep its double electric motors running for over 24 hours in the right conditions.
A small 20-kWh lithium-ion battery offers backup power. But on this flight, Domjan relied almost entirely on sunlight and thermals rising from the warm August ground. A variable-pitch propeller, recently added to the aircraft, helped optimize performance in the thin air.
The cockpit remains unpressurized, meaning Domjan required a specialized suit that pumped in oxygen and protected him from temperatures near -70°C. At such heights, even small technical issues could become deadly. But the flight went smoothly, with the aircraft registering more than 100 total flight hours by the end of July, despite its experimental status.
SolarStratos now hopes to go higher still. The ultimate goal is to reach the stratosphere, somewhere around 25,000 meters (82,000 feet) altitude. The upcoming “stratospheric odyssey,” as the team calls it, will include atmospheric measurements to aid scientists studying the upper atmosphere and climate change.
Why This Matters
Solar flight is not new. In 2016, Solar Impulse 2 completed the first round-the-world flight powered only by the sun. But that aircraft required a full team and years of planning. What’s different about SolarStratos is its elegance: a single pilot, a light frame, and the promise of regular high-altitude clean flights.
Domjan, known for leading PlanetSolar, the first solar-powered boat to circumnavigate the globe, has spent years championing solar mobility. His work is a response to the aviation industry’s carbon footprint, which accounts for roughly 2.5% of global CO₂ emissions.
As regulators begin to catch up, the timing couldn’t be better. The FAA recently expanded its rules for light sport aircraft to include electric and hydrogen propulsion. In the U.S., the White House has also announced policies to boost electric flight and remove bans on supersonic travel. These changes open the door for technologies like SolarStratos to take flight commercially, although using an exclusively solar-powered plane has very limited uses. The generated power cannot carry more than a handful of people, let alone cargo.
Domjan’s flight was about showing what can be done with sunlight, innovation, and a refusal to accept the limits of the past.
Whether SolarStratos ever hits 25,000 meters remains to be seen. But its message has already landed: Clean aviation is no longer a fantasy. It’s just getting off the ground.
