Joby Aviation, the S Four eVTOL, and the FAA Powered-Lift Certification Gauntlet That Has Put an Electric Air Taxi Closer to Your Airport Than Most Pilots Realize

Joby Aviation’s S4 has become the first eVTOL aircraft to complete all staged FAA type certification milestones - a regulatory achievement no competitor has matched. The aircraft already flies under an FAA Special Airworthiness Certificate, carrying a pilot and up to four passengers at 150 mph over a range of approximately 150 miles on a single charge. A type certificate, the final step unlocking commercial passenger operations, is not yet in hand, but the certification progress is real, documented, and ahead of every other program in this category.

How the Joby S4 Works

The S4 uses six electric motors driving six propellers that tilt. At takeoff, all six point straight up, lifting the aircraft like a large multirotor. As it accelerates into forward flight, the propellers rotate until they face forward like conventional tractor propellers on a fixed-wing aircraft. At that point, the wing takes over lift generation and the motors drop to a fraction of their hover power demand.

This transition architecture is what separates Joby from most other eVTOL designs. Pure multirotors hover on thrust alone, burning energy at a brutal rate. In fixed-wing cruise, the wing carries the load and the motors only overcome drag. That energy shift is how a 150-mile range becomes achievable - compared to the 30 to 40 miles a non-transitioning multirotor design can manage.

Why the Joby S4’s Noise Profile Matters

Flyover noise measurements have come in around 45 decibels - quieter than the ambient noise level of most city streets. That figure is engineered, not incidental, through deliberate choices in blade count, diameter, and tip speed.

Noise is not a marketing differentiator for eVTOL operators. It is a certification requirement, a community acceptance question, and the variable that determines whether vertiports get approved near the urban centers they are designed to serve. Getting the acoustic signature right was not optional for commercial viability.

A Development Timeline Most People Miss

Joby Aviation was founded in 2009 by JoeBen Bevirt in Santa Cruz, California. For most of the following decade, the company was largely invisible to the aviation press - iterating on configurations, running small-scale tests, and accumulating flight data while competitors were still writing white papers.

By the time eVTOL became a media phenomenon around 2017–2018, Joby had years of flight test data that other programs were just beginning to accumulate. The S4 flying today is the product of multiple design generations, not a first-attempt prototype. That head start explains much of their certification lead.

Joby entered a type certification agreement with the FAA in 2018 and has since worked through every staged milestone in the FAA’s compliance framework - the first eVTOL program to do so.

Why FAA Powered-Lift Certification Is Unprecedented

The FAA faced a foundational regulatory question before Joby’s certification could begin: what category does an eVTOL belong to? It is not a helicopter under Part 27. It is not a fixed-wing airplane under Part 23. It is a powered-lift aircraft - a category that existed in the FARs but had never been used to certify a commercially operated passenger vehicle.

The agency built a Means of Compliance framework drawing on Part 23 standards, augmented with special conditions addressing powered-lift-specific requirements like the vertical-to-forward-flight transition. That framework had to be created from scratch and applied to an aircraft category for the first time.

Completing the staged milestones does not equal holding a type certificate. The type certificate requires a completed conforming production aircraft and full compliance documentation - work that is ongoing. But clearing the entire staged sequence ahead of every competitor is a significant technical and regulatory milestone the industry has been watching closely.

The Investment Behind Joby Aviation

This is a capital-intensive program, and the funding reflects confidence from credible partners.

Toyota has invested over $600 million across multiple rounds. Delta Air Lines committed $200 million and announced a partnership to integrate air taxi routes with passenger connections at major airports. Joby went public through a SPAC in 2021, and in 2020 acquired Uber Elevate - Uber’s urban air mobility division - bringing engineering talent, route economics research, and letters of intent with cities and airports.

The U.S. Air Force’s Agility Prime program contracted with Joby for flight demonstrations and data sharing, providing a funded pathway to continue generating certification-quality flight data during the years before commercial revenue was possible. Joby has accumulated hundreds of flight test hours at their facility in Marina, California and at Edwards Air Force Base.

What Are the Real Limits of Electric Aviation?

Battery energy density is the hard ceiling every electric aviation program runs into. The best lithium-based cells available today store approximately 250–300 watt-hours per kilogram. Jet fuel stores approximately 12,000 watt-hours per kilogram. That gap is not an engineering problem - it is a chemistry difference no software update addresses.

Joby’s 150-mile range sits at the ceiling of what current battery technology delivers, not a conservative estimate. In actual commercial operations, weather deviations, headwinds, reserve requirements, and payload all reduce the usable route radius considerably. The realistic commercial application is city-center to airport, closely spaced metro areas, or business district to medical center. Those markets have real value, but they represent a narrow slice of aviation until battery chemistry improves.

Battery degradation over charge cycles adds another operational variable. Lithium cells lose capacity as they age, and an aircraft flying dozens of revenue cycles per day will wear through battery packs far faster than one making occasional training flights. Joby has not published detailed specifications for expected battery service life under commercial operational conditions - a number that will matter significantly to anyone modeling fleet economics.

Why Vertiport Infrastructure Is the Hidden Bottleneck

Joby’s business model requires a network of vertiports - vertical takeoff and landing facilities with fast-charging infrastructure and passenger handling capabilities. These are not helicopter pads. They require electrical infrastructure capable of rapid turnarounds, physical space to handle multiple aircraft without conflict, and local government approval to exist near the urban centers the routes are meant to connect.

Joby has announced partnerships with airports and real estate developers for vertiport sites. The network is not yet built. Constructing it requires coordination, capital, and regulatory approvals that the aircraft certification program does not cover. The infrastructure timeline runs on its own clock, independent of where the type certificate process stands.

What eVTOL Means for Pilots and Airspace

Low-altitude urban eVTOL operations will sit alongside existing VFR traffic, instrument approaches, and potentially new airspace designations the FAA has not yet written. The agency has been developing a concept of operations document for urban air mobility covering how eVTOLs, drones, and conventional aircraft share the low-altitude urban environment.

How that framework translates into actual NOTAMs, airspace designations, and controller procedures is still being worked out. No one has fully answered how a tower sequences an eVTOL on a city route alongside approach traffic at a Class B airport during an IFR day. The engineering answers exist. The regulatory answers are still being written, and that process runs parallel to aircraft certification without necessarily synchronizing with it.

Who Are Joby’s Competitors?

Archer Aviation, based in San Jose, is the closest competitor on certification timeline. Their Midnight aircraft uses 12 propellers and has been in a test program since 2022. They have manufacturing support from Stellantis and pre-orders from United Airlines. Their certification progress trails Joby’s, but the program is well-funded and active.

Lilium, the German eVTOL company, filed for insolvency in 2024 before a new investor group acquired the program. Their design embedded electric fans inside wing and canard surfaces rather than using external propellers - technically ambitious, but it created energy requirements that current battery chemistry couldn’t meet at commercial scale. The Lilium situation is a clear reminder that novel engineering and substantial funding do not guarantee survival when physics create a ceiling a design cannot clear.

Vertical Aerospace in the United Kingdom is developing the VX4 with American Airlines pre-orders. Their test program has encountered setbacks, but development continues.

The industry-wide pattern is that commercial timelines have slipped. Initial projections from around 2018 suggested revenue operations by 2024–2025. The realistic timeline is now 2026–2028 for the first companies to achieve a type certificate and begin commercial service. Joby has cited the 2028 Los Angeles Olympics as a target for beginning California service - aggressive given current certification status, but not impossible.

Key Takeaways

Joby Aviation has completed all staged FAA powered-lift certification milestones, making the S4 the furthest-along eVTOL program in the world - but a full type certificate has not yet been issued and requires a conforming production aircraft and complete compliance documentation.
The tilting-rotor architecture enables a ~150-mile range and near-silent flyover noise (~45 dB), both essential for commercial viability in urban environments - and neither is achievable with a conventional multirotor design.
Battery chemistry is the hard ceiling: at ~250–300 Wh/kg versus jet fuel’s ~12,000 Wh/kg, electric aviation is viable for short-range urban routes only, and real-world payload and weather reserves shrink that range further.
Joby’s funding is substantial - over $600 million from Toyota, $200 million from Delta, and backing from the U.S. Air Force’s Agility Prime program - providing the runway to complete certification without commercial revenue.
The airspace integration question remains unresolved: pilots should expect new airspace structures, ATC procedures, and operational rules for low-altitude urban eVTOL traffic. The next major certification milestone to watch is production conforming aircraft and full compliance findings - when those happen, this becomes an airspace story as much as a technology story.