Joby Aviation, the S4 Air Taxi, and What FAA Certification Actually Demands Before an eVTOL Carries a Paying Passenger

Joby Aviation is closer than any other company to putting a fare-paying passenger into an electric air taxi. With more than $2 billion raised, an active FAA type certification program, and a Part 135 air carrier certificate already in hand, Joby has built the most complete regulatory and operational foundation in the eVTOL industry. What that journey actually required - technically, legally, and physically - is a more demanding story than the company’s marketing suggests.

Who Built Joby and Why the Starting Point Matters

JoeBen Bevirt founded Joby Aviation in 2009, working from a property in the Santa Cruz mountains, California. His core design premise was different from every other aircraft program of that era: rather than adapting an existing airframe to electric power, he wanted to design an aircraft that assumed electric motors from the beginning.

That distinction has real engineering consequences. Electric motors deliver instant, predictable torque across a wide range of conditions - no combustion vibration, no power curve degradation with altitude and temperature. More importantly, they can be made small enough to run many simultaneously across an airframe, which changes what flight control architectures are possible.

A six-motor distributed layout gives you six independent control points. You can use differential thrust the way a fixed-wing pilot uses ailerons. You can design for motor failures not as emergencies but as anticipated, managed events. These configurations were aerodynamically possible before electric motors - the control authority to make them safe was not.

How Joby Got Funded: Google, Toyota, United, and the Air Force

Joby worked in relative obscurity for years - aerodynamic research, small test vehicles, an extensive patent portfolio. The company’s public profile changed when Google’s venture arm invested around 2016.

Toyota followed with a partnership announced in 2020, committing several hundred million dollars. The strategic value was not just capital. Toyota brought manufacturing knowledge - specifically, the institutional expertise required to close the gap between prototype and production. That transition has ended more promising aircraft programs than any certification challenge. It is not the kind of knowledge you acquire from a venture fund.

United Airlines committed to purchase 100 aircraft, with options for another 100. The U.S. Air Force evaluated the aircraft at Edwards Air Force Base, California. Joby went public via a SPAC in 2021 and trades on the New York Stock Exchange.

What the S4 Actually Is

The Joby S4 carries one pilot and four passengers, with roughly the footprint of a large SUV. It has six tilting rotors, each driven by its own independent electric motor. In hover, the rotors point upward and function like helicopter rotors. In cruise, they tilt forward and function like conventional propellers.

Tilt-rotor technology dates to the Bell XV-3 in the 1950s. The Bell Boeing V-22 Osprey is the most familiar operational example. What Joby adds is a six-motor layout that provides redundancy a twin-engine tilt-rotor cannot match. If one motor fails, the flight control system compensates automatically using the remaining five - faster than any human pilot could respond.

In cruise mode, the propeller blades fold back to reduce drag. The aircraft effectively becomes a fixed-wing airplane, which is how it reaches a published top speed of approximately 200 mph - roughly 110 mph faster than a Cessna 172. Published range is approximately 150 miles.

The cockpit uses fly-by-wire controls in a sidestick configuration. The aircraft is designed to be flyable by a commercial pilot with type-specific training, not a traditional helicopter pilot. That matters for the operational model: the pool of rated helicopter pilots is small and expensive. Fixed-wing pilots trained on the type gives operators a significantly larger crew base.

Why Noise Is Not Just a Marketing Feature

Joby claims dramatically lower acoustic signatures than conventional rotorcraft during takeoff and approach. The physics support the claim directionally: smaller rotors at lower tip speeds are inherently quieter than a large-disc helicopter main rotor, and six distributed rotors spread the acoustic footprint differently than a single rotor.

Whether the specific numbers survive full independent certification testing remains to be seen. But the stakes are real. Helicopter commuter services operated profitably in New York in the 1980s. They were eventually shut down by noise complaints and local political pressure. The eVTOL industry is fully aware of that history, and noise engineering is not incidental to the business case - it is central to it.

How the FAA Is Certifying Something That Has No Existing Category

The FAA’s existing certification framework was written for two types of aircraft: fixed-wing (Part 23 and Part 25) and rotorcraft (Part 27 and Part 29). None of those categories adequately address a tilting-rotor, distributed-electric, software-managed flight control aircraft.

The FAA’s response is to issue special conditions - tailored requirements written specifically for novel design features that existing regulations don’t cover. This is not a rubber-stamp process. It is a documented technical negotiation, published in the Federal Register, and time-consuming by design.

Joby received a G-1 Issue Paper from the FAA, which establishes the certification basis: which existing regulations apply, what special conditions govern novel features, and what means of compliance the FAA will accept. The G-1 Issue Paper is not the finish line. It is the starting gun. It defines what the certification race course looks like.

Joby has completed the planning and safety framework stages and is now in active compliance demonstration work - ground loads testing, structural fatigue testing, electromagnetic compatibility evaluation, and flight testing in increasingly demanding conditions including deliberate failure-mode scenarios.

The Software Certification Challenge

The flight control software managing six motors - maintaining trim authority through a motor failure, handling the aerodynamic transition between hover and cruise, doing all of this with certified redundancy - is primarily a software and systems engineering challenge, not a mechanical one.

The applicable standard is DO-178C, the FAA’s airborne software certification guidance. The novelty of the platform means a significant portion of compliance work is being developed for the first time, in real time, with active FAA technical staff involvement. There is no existing precedent to apply. That takes longer than referencing prior certification programs.

The FAA issued Joby a Special Airworthiness Certificate in the experimental category, allowing flight testing before type certification is complete. By early 2024, Joby had logged more than 1,000 test flights across multiple prototype aircraft.

The Part 135 Certificate and Why Joby Got It Early

In 2022, Joby became the first eVTOL company to receive a Part 135 air carrier certificate under Federal Aviation Regulations. Part 135 governs on-demand air taxi operations.

Obtaining that operational certificate before type certification was deliberate. The safety management system, pilot training curriculum, maintenance procedures, and operational control framework all get developed and examined in parallel with the aircraft engineering work. When the type certificate arrives, the operational infrastructure is not starting from scratch.

The difference between a certification program that takes nine years and one that takes twelve often comes down to whether an applicant is managing one complex problem at a time or two simultaneously. Joby made the two-at-once choice early.

The Battery Physics Problem No One Can Engineer Around Yet

Jet fuel carries roughly 40 times more energy per kilogram than the best commercially available battery cells. That gap explains everything about the eVTOL business model: the focus on short urban routes, the 15-to-30-mile range targets, the city-center-to-airport use cases. The physics work in the aircraft’s favor on those routes. They do not work elsewhere.

Battery energy density has improved at approximately 3–5% per year over the last decade. Solid-state battery technology - still several years from commercial-scale production - could represent a more significant improvement if laboratory specifications translate to production cells. Second and third generation eVTOL aircraft are contingent on that chemistry development arriving close to schedule. The first generation is being certified around the chemistry that exists today, which is the correct approach: certify what you can certify, and improve from there.

The Competitive Landscape

Archer Aviation, based in San Jose, California, is building the Midnight - a 12-motor aircraft carrying one pilot and four passengers, with a range and speed envelope similar to the S4. Archer also has a relationship with United Airlines. Its certification timeline runs roughly parallel to Joby, perhaps a year or more behind in total program maturity.

Lilium, a German company, pursued a different architecture: dozens of small electric fans embedded in wing structure for vectored thrust. The company entered bankruptcy in late 2024. The aircraft program was subsequently acquired and relaunched under new ownership. The bankruptcy reflected a specific capitalization failure, not a verdict on eVTOL as a category.

Wisk Aero, backed by Boeing and Google, is pursuing a fully autonomous air taxi - no pilot aboard. That is a significantly more complex regulatory challenge, and their timeline extends well beyond where Joby and Archer are today. The FAA does not currently have a framework for certifying autonomous passenger-carrying aircraft for commercial use.

What 2026 Commercial Service Actually Looks Like

If Joby achieves type certification and begins commercial service in 2026, initial operations will almost certainly involve a small number of routes in a small number of cities. Los Angeles, San Francisco, and New York are the most commonly discussed candidates - markets where landing infrastructure can be built, where per-seat pricing can be justified by travel time savings, and where early adopters will pay a premium for the proposition.

The piece that receives less attention is the vertiport problem. Aircraft certification and an air carrier certificate solve the sky side of the equation. Landing in a dense urban environment requires real estate, zoning approvals, fire safety compliance, and noise compatibility studies. None of those are resolved by the FAA, and none of them move at the pace of an engineering program. The urban planning infrastructure for this business model to scale is still in early development and may ultimately set the pace of growth more than aircraft certification does.

Why This Matters for Pilots Today

The avionics technology being developed for eVTOL - advanced flight control software, sensor fusion for navigation, battery management systems - will diffuse into general aviation on the same path that military avionics technology has always followed, just from a different direction.

Understanding fly-by-wire control envelopes, energy management in battery-powered aircraft, and highly integrated flight control systems are skills that will become increasingly relevant to working pilots. The aircraft being built now are not designed to eliminate aviators. They are designed to make a new category of air transportation commercially viable.

Key Takeaways

Joby Aviation has raised more than $2 billion, holds a Part 135 air carrier certificate (the first ever for an eVTOL company), and has completed 1,000+ test flights as of early 2024, making it the most advanced eVTOL certification program currently active.
The S4 carries one pilot and four passengers, uses six tilting rotors, reaches approximately 200 mph in cruise, and is designed to be operated by fixed-wing commercial pilots - not rotorcraft specialists.
FAA certification requires special conditions because no existing regulatory category covers a distributed-electric, tilting-rotor, software-managed aircraft; the process involves novel compliance work being developed in real time with active FAA technical involvement.
Battery energy density - roughly 40 times lower per kilogram than jet fuel - is a hard physics constraint that shapes the entire eVTOL business model around short urban routes, and no current engineering can eliminate that constraint.
The vertiport infrastructure problem (real estate, zoning, fire codes, noise compatibility) may determine the pace of commercial scaling more than aircraft certification timelines, and it currently lags the aviation engineering work significantly.