When electric aircraft developer Joby Aviation in August unveiled its concept for a hybrid-powered, optionally piloted variant of its electric vertical takeoff and landing (eVTOL) S4 air taxi, it predicted first flight before the end of 2025.
Ultimately, that milestone took just three months.
Joby on Thursday said a demonstrator aircraft—an S4 integrated with a turbine-electric powertrain and the company’s proprietary autonomy system—made its maiden voyage last week in Marina, California.
In August, Joby and L3Harris, which will handle the integration of the aircraft’s sensors, effectors, and communication systems, said they would pursue defense applications for the model. It is expected to offer improved range and payload compared to the S4, which is designed for a pilot to fly up to four passengers as far as 130 nm.
“It’s imperative that we find ways to deliver new technology into the hands of American troops more quickly and cost-efficiently than we have in the past,” JoeBen Bevirt, CEO and founder of Joby, said Thursday. “Our vertical integration puts us in a unique position to deliver on this goal, moving from concept to demonstration—and from demonstration to deployment—at a pace that is unprecedented in today’s aerospace and defense industry.”
Joby said it plans to continue ground and flight testing the demonstrator ahead of planned exercises with unnamed government customers in 2026. L3Harris intends to equip it specifically for low-altitude defense applications such as logistics.
The autonomous aircraft, initially billed as “optionally piloted,” could even serve as a “loyal wingman” for crewed aircraft, akin to the Air Force’s Collaborative Combat Aircraft (CCA) framework. It incorporates Joby’s Superpilot, which it acquired from Xwing in 2024.
In July, a Superpilot-equipped Cessna 208 logged more than 7,000 autonomous miles during a military exercise near Hawaii—including a nearly 5,000-mile round-trip ferry flight across open ocean. The Cessna handled mission profiles from cargo delivery to intelligence, surveillance, and reconnaissance in Class B, C, D, and uncontrolled airspace, as well as VFR and IFR conditions. It was managed primarily from more than 3,000 miles away in Guam.
By assigning autonomous aircraft to urgent or high-risk missions, the military could free up larger and more expensive aircraft for more suitable tasks. Hybrid propulsion could give Joby’s concept the necessary range to cross the Pacific. And with VTOL capability, it is runway independent.
According to Joby, the U.S. government is seeking about $9 billion for next-generation autonomous and hybrid aircraft platforms in its fiscal year 2026 budget.
“Recent conflicts have certainly shown that the sort of paradigm of large, expensive, crewed helicopters for a wide variety of missions may not be the right one,” said Paul Sciarra, executive chairman of Joby, during the company’s second-quarter earnings call in August. “So we think we’ve got an opportunity in conjunction with L3[Harris] to essentially build something that is cheaper, quieter, autonomous, and essentially flexible for a wide range of use cases.”
Joby’s Dual-Use Strategy
Though it is billed primarily for defense, Joby on Thursday said the hybrid concept could handle “longer range air taxi services” and be sold to civilian and commercial customers.
It could also catalyze the company’s adoption of autonomy on the S4, which will initially have an onboard pilot.
“We recognize that a future generation of autonomous aircraft will play an important part in unlocking our vision of making clean and affordable aerial mobility as accessible as possible,” Bevirt said after the acquisition of Xwing’s Superpilot last year.
Joby on Thursday said S4 prototypes have surpassed 50,000 hours of flight testing. But commercial operations—such as the home-to-airport air taxi services the company envisions—are far from an ideal testing ground for a technology as novel as autonomy.
The military, though, can take on that risk. It has already conducted multiple operational demonstrations with Superpilot-equipped aircraft. By developing a defense variant for the military, Joby could evaluate autonomy in the field and get a better sense of how it may translate to its air taxi.
The S4 is designed for urban trips with up to four passengers, with a cruise speed of about 200 mph. Its six electric motors power six tilting propellers on the aircraft’s fixed wing and V-tail, producing significantly less noise than a helicopter.
Joby is also developing a liquid hydrogen-powered S4 variant for regional operations. Both could benefit from the validation of autonomy on the hybrid concept.
“Our partners can rapidly deliver new capabilities for the Department of War while we benefit from advancing the maturity of our hybrid and autonomous systems,” said Bevirt. “In turn, this will help pave the way for commercial applications, from longer-range hybrid VTOL missions to autonomous air operations in commercial airspace.”
