Combine the Joby S4 pre-production prototype with H2 Fly’s expertise in providing clean energy, and watch world records fall.
2021 155-Mile Battery Flight
Justin Paines, Joby’s Chief Test Pilot, guided the eVTOL through eleven circuits of a pre-designated route and managed 154.6 miles (248.8 km) in just 77 minutes.
JoeBen Bevirt, Joby’s founder, noted his firm had, “achieved something that many thought impossible with today’s battery technology.” Batteries have improved since then, but an alliance with a German hydrogen program makes even longer flights possible.
2024’s Hydrogen Odyssey
In an even greater demonstration of its capabilities, an S4 powered by hydrogen managed a 523 mile, non-stop flight on June 24, 2024. Powering around a circuit above Marina, California, the craft landed with 10 percent of its 40-kilogram (88 pound) hydrogen load still available.
A collaboration between Joby and Germany’s H2-Fly uses much of the same system as H2-Fly’s Hy4 aircraft, a re-engineering of the G4 designed by Tine Tomažič, head of engineering and programs at Pipistrel. It won the 2011 NASA Green Flight Challenge sponsored by Google, achieving the energy equivalent of 403.5 mpg.
Since that achievement, the craft has been converted to fly on hydrogen, essentially doubling its range. Similar results have been achieved with hydrogen on the Joby S4.

On June 24, 2024, Joby’s hydrogen-electric technology demonstrator aircraft completed a 523-mile flight above Marina, California, with no in-flight emissions except water vapor. Note the added components for the H2-powered craft. llustration: Joby Aviation
JoeBen Bevirt, Founder and CEO of Joby, explains, “Traveling by air is central to human progress, but we need to find ways to make it cleaner. With our battery-electric air taxi set to fundamentally change the way we move around cities, we’re excited to now be building a technology stack that could redefine regional travel using hydrogen-electric aircraft.
“Imagine being able to fly from San Francisco to San Diego, Boston to Baltimore, or Nashville to New Orleans without the need to go to an airport and with no emissions except water. That world is closer than ever, and the progress we’ve made towards certifying the battery-electric version of our aircraft gives us a great head start as we look ahead to making hydrogen-electric flight a reality.”
With a majority of design, testing, and certification work completed on the battery-powered version of the S4, the hydrogen-powered version will be able to use the same infrastructure and Joby’s ElevateOS software.
Joby’s hydrogen-electric demonstrator is part of the Company’s future technology program and is the result of several years of collaboration between a small team at Joby and H2FLY, Joby’s wholly-owned subsidiary based in Stuttgart, Germany. The converted aircraft previously completed more than 25,000 miles of testing as a battery-electric aircraft at Joby’s base in Marina, CA.

Joby/H2Fly’s Hy4 on one of its many long-range flights. As G4, the two-fuselage craft won 2011’s Green Flight Challenge.
Joby’s H2FLY team used similar technology to complete another record-breaking flight in September 2023, when they flew the world’s first piloted flight of a conventional liquid hydrogen-electric aircraft using their fuel cell technology.
Good Reporting and Splendid Reader Comments
Green Car Congress provided one of the sources for this blog entry, but some of their well-informed readers supplied multiple details on the engineering involved. See this array of thoughtful material from DaveMart, Roger Brown, and Roger Pham. They include several references to additional enlightening material.
Joby and H2Fly have added substantial range to both rotary-wing and fixed-wing aircraft with H2 power. The move from Urban Air Mobility to Regional Air Mobility may be one of the most important moves clean aviation can make. More people are moving to further distant exurbs, the cost of housing becoming somewhat staggering in major cities. Means of providing relatively inexpensive commutes for these people will become a prime concern in the near future.