Joby's S Four, the FAA Powered-Lift Certificate, and the Real Distance Between Air Taxi Hype and Your City's Skyline

Joby Aviation’s S4 eVTOL aircraft exists, flies, and is held by a company that received an FAA air carrier certificate in spring 2025. The type certificate that would allow paying passengers is still pending, and the surrounding infrastructure - vertiports, training pipelines, airspace procedures - is incomplete. The gap between working technology and commercial air taxi service is real, but it is an infrastructure gap, not an engineering one.

What Is the Joby S4 and How Does It Fly?

The Joby S4 is an electric vertical takeoff and landing (eVTOL) aircraft built around six tilting rotors mounted along a fixed wing. At low speed, the rotors point upward and provide direct lift, like a helicopter. As the aircraft accelerates, they tilt forward and transition to conventional propulsion while the fixed wing takes over generating lift. Between those two modes lies a transition phase - and that is where the real engineering challenge lives.

Managing that transition means the flight control software is simultaneously running six independent electric motors, each with its own rotor, while the aerodynamic environment changes second by second as airspeed builds. The aircraft must be stable in helicopter mode, stable in fixed-wing cruise, and controllable during the handoff between them. If a rotor fails during transition, the control laws must compensate using the remaining five fast enough that the pilot never needs to intervene.

That is not a design goal. It is the certification standard. Joby has been working on this specific problem since 2009, long before eVTOL became a venture capital category.

What Are the S4’s Published Performance Numbers?

The S4’s specifications hold up to scrutiny:

Top cruise speed: 200 mph
Useful range: approximately 100 miles on a full charge
Passenger capacity: four, plus pilot
Approach noise: approximately 45 decibels - comparable to a dishwasher or quiet library

That noise figure is operationally significant. A conventional helicopter on approach typically exceeds 80 decibels. In urban environments, that noise signature is a hard constraint - helicopter services cannot operate over residential areas at all hours. The S4’s acoustic profile is what makes urban air mobility practically urban rather than just theoretically so.

Why Does 100 Miles of Range Actually Work?

Lithium-ion batteries store roughly 40 times less energy per kilogram than jet fuel. That is a chemistry problem, not a near-term engineering fix, which means electric aircraft at this scale will always optimize for shorter, high-frequency routes rather than long cross-countries.

But 100 miles is well-matched to the actual use case. Los Angeles to San Diego. Manhattan to Newark. Downtown to the airport. These are routes where the time savings over ground transport are enormous and where 100 miles is more than sufficient. The S4 is not competing with a turboprop on a 250-mile route. It is competing with a car on a 40-mile route, and for that mission, the range math works.

How Is the S4’s Redundancy Architecture Different?

Rather than one large battery pack, the S4 uses multiple distributed battery modules, each feeding a separate motor controller running a separate rotor. A failure in one module does not cascade to the others.

This is a structurally different failure mode than a combustion engine losing power. The distributed electric approach creates its own challenges - thermal management, weight balance, turnaround charging time - but the single-point-of-failure risk profile is more favorable than a traditional powertrain.

Where Does Joby Stand on FAA Certification?

By early 2025, Joby had completed more than 1,000 test flights. The company’s investors include Toyota and, through a commercial partnership targeting airport-to-city routes, Delta Air Lines. The U.S. Air Force holds contracts with Joby through its Agility Prime program, a Pentagon effort to accelerate eVTOL development for military logistics applications.

In spring 2025, the FAA issued Joby an air carrier certificate - the operational certificate required to carry paying passengers commercially. Joby does not yet hold a type-certified aircraft, but the company operating it is already certified as a carrier. That is an unusual sequence, and it signals that the FAA is treating this as a serious commercial operation, not a research program.

The type certificate itself is still pending, and the reasons are worth understanding.

Why Did the FAA Need to Create a New Pilot Certificate Category?

The FAA governs powered commercial aircraft under two main standards: Part 23 for normal-category airplanes (Cessna 172, Cirrus SR22) and Part 29 for transport-category rotorcraft. The S4 is neither. It takes off like a helicopter, cruises like an airplane, and runs on electric motors that create failure modes with no precedent in either standard.

The powered-lift category has technically existed in the Federal Aviation Regulations for decades, but it never had a clean certification pathway because there were never enough powered-lift aircraft to justify building one. In 2024, the FAA published a final rule establishing a new pilot certificate specifically for powered-lift operations - new training standards, new currency requirements, new medical framework. This was the first new pilot certificate category the FAA has created in a very long time.

For Joby’s type certificate specifically, the FAA assigned a certification basis drawing from both Part 23 and Part 29 simultaneously, with adaptations written specifically for powered-lift characteristics. Satisfying modified versions of two regulatory regimes designed for aircraft the S4 is not accounts for a significant portion of the certification delays.

This pattern is not new. Glass cockpits in general aviation required the FAA to develop entirely new certification standards for digital flight instruments before manufacturers could install them legally in certified aircraft. ADS-B Out was mandated in 2020, but equipment certification stretched over more than a decade before that deadline. Technology moves faster than the regulatory system. The system eventually catches up.

Joby’s original projection was certification in 2023, revised to 2024, with the current working estimate at 2025 or 2026. Based on publicly available information about where the certification process stands, 2026 for a type certificate and 2027 before a paying passenger books a seat through a real commercial operation is the more realistic estimate.

What Happened to the Rest of the eVTOL Industry?

The eVTOL investment boom of 2020 and 2021 brought dozens of companies public through special purpose acquisition vehicles. The projections embedded in those deals were significantly disconnected from realistic certification timelines, and the field has consolidated accordingly.

Lilium, the German company pursuing a jet-powered eVTOL using distributed electric fans rather than rotors, declared bankruptcy in 2024. A partial rescue by new investors has it attempting a comeback, but the path is unclear. Overair shut down entirely.

The companies still actively flying in 2025:

Archer Aviation - Midnight aircraft has completed a substantial flight test campaign and carries a commercial agreement with United Airlines
Wisk Aero (backed by Boeing) - has pivoted to a fully autonomous, no-pilot concept and is using New Zealand as a testbed market before pursuing U.S. certification
Beta Technologies (Vermont) - building both fixed-wing and tilt-rotor electric aircraft while simultaneously building their own fast-charging infrastructure; holds logistics contracts with UPS

Joby leads on flight hours, certification progress, and aircraft maturity. But the competitive landscape in 2025 looks nothing like the 20-aircraft race drawing headlines four years ago.

What Infrastructure Does an Air Taxi Network Actually Require?

The aircraft being certified and the system being ready are two different problems. A commercial air taxi network requires:

Certified landing facilities. Vertiports - pads sized for eVTOL aircraft - need approach and departure procedures, separation standards, and charging systems capable of turning an aircraft around in the time it takes passengers to board and deplane. If a 45-minute charge is required for a 40-minute flight, the utilization economics collapse.

Maintenance infrastructure. Mechanics trained in lithium battery systems, electric motor overhaul, and the specific redundancy architecture of each aircraft type do not currently exist at scale.

Airspace integration. Terminal control areas are already among the most complex managed airspace in the system. Adding a new aircraft category with different performance characteristics and potentially high-frequency operations requires coordination between the FAA and local authorities that is ongoing and not finished.

Legal and financial frameworks. Insurance products for this aircraft category are still being written. Fire suppression standards for lithium battery charging in proximity to occupied buildings are still being developed.

Delta’s partnership with Joby is actively working through what a vertiport embedded in or adjacent to a major airport terminal physically looks like. That means solving a TSA security problem (passengers who have cleared screening cannot mix with those who haven’t), a real estate problem, and a noise impact assessment problem - all simultaneously.

What Does the Powered-Lift Certificate Mean for Pilots Today?

The powered-lift pilot certificate exists in the regulatory framework. The training ecosystem to deliver it at scale does not yet exist.

When Joby begins commercial operations, it will train pilots internally, the way airlines have historically built their own pipelines. For pilots holding existing airplane ratings, the FAA’s framework includes credit pathways - this is not starting from zero. But it is a meaningful qualification, not an endorsement added in an afternoon.

The powered-lift certificate requires demonstrated proficiency across three distinct flight regimes: vertical takeoff and landing mode, fixed-wing cruise mode, and the transition between them. That transition phase is where the aircraft’s behavior is most complex and where training standards are appropriately most demanding. The S4’s control laws during transition have no close analogue in existing civil aviation training. New simulators, new curricula, and new instructor certification programs are being built. None of it is available at scale.

If eVTOL operations mature into a commercial aviation segment the way regional aviation did, the demand for pilots holding powered-lift certificates will eventually be significant. The parallel is not exact, but it rhymes: the category starts small, in specific markets, with proprietary pipelines - then scales, and the certificate becomes a standard qualification the broader training ecosystem delivers. That process takes a decade, not a year.

Key Takeaways

The Joby S4 is a real, flying aircraft with six tilting rotors, a 200 mph cruise speed, ~100 mile range, four passenger seats, and an approach noise level of ~45 dB - roughly half the decibel level of a conventional helicopter.
Joby received an FAA air carrier certificate in spring 2025, a meaningful regulatory milestone; the type certificate allowing revenue passengers is still pending, with a realistic estimate of 2026 for certification and 2027 for commercial operations.
The FAA’s 2024 powered-lift final rule created the first new pilot certificate category in decades - existing rated pilots have credit pathways, but this is a substantive qualification requiring proficiency across three distinct flight regimes.
The eVTOL field has consolidated sharply since the SPAC boom of 2020–2021; Lilium filed bankruptcy in 2024, while Archer, Wisk, and Beta Technologies remain active alongside Joby.
The critical open problems are infrastructure, not aircraft engineering: vertiports, charging turnaround times, airspace integration, maintenance training, and insurance frameworks are all still being built out.