Joby Aviation’s Tier 1 Supply Chain: Who Builds the eVTOL and What It Demands

Joby Aviation is building an aircraft that does not fit neatly into any existing regulatory box. Its S4 eVTOL — six tilting rotors, distributed electric propulsion, designed for FAA Part 135 commercial air taxi operations — is being certified under a G-1 issue paper process that requires Joby and the FAA to jointly define the means of compliance for technologies with no direct precedent. That process is hard enough for the OEM. For Tier 1 suppliers asked to develop novel components to specifications that are themselves still being negotiated with a regulator, it is a different order of engineering difficulty.

Understanding who supplies Joby, what they are being asked to deliver, and where the systems engineering friction concentrates is increasingly relevant as the program moves from development into the sustained airworthiness and manufacturing readiness phases that precede entry into service.

The Motor Suppliers: Custom Machines Under Real-Time Specification Pressure

Joby’s distributed electric propulsion architecture uses twelve motors — two per rotor across six tilt-rotor assemblies — in a configuration where motor failure modes directly affect airworthiness. This is not a commodity procurement. The motors are high-speed, high-pole-count permanent magnet synchronous machines optimized for the weight, efficiency, and fault-tolerance envelope Joby has defined at the aircraft level.

Joby has publicly disclosed a significant internal motor development capability, and key motor winding and magnetic design work appears to be conducted in-house or through closely-held partnerships rather than commodity supplier relationships. This is consistent with the strategy of protecting core propulsion IP while limiting ITAR exposure — permanent magnet motor designs with performance envelopes exceeding certain thresholds are controlled under ITAR Category VIII and XV, depending on application classification.

The systems engineering challenge this creates is real. Motor suppliers or co-developers must deliver electrical interface specifications, thermal models, failure mode and effects analyses (FMEAs), and software interfaces for motor controllers — all at a level of maturity that supports aircraft-level safety analysis — while the aircraft’s power distribution architecture is still being validated. Requirements flow-down in this environment is inherently iterative. A change to the battery pack’s discharge profile propagates through the power electronics to the motor operating envelope. A change to the aircraft’s weight budget propagates to motor torque-to-weight ratios. Suppliers working on fixed contracted specifications face real schedule risk when the upstream system is still in motion.

Battery Pack Developers: Novel Chemistry, Aggressive Certification Demands

Joby’s battery technology is one of its most publicly-discussed competitive differentiators. The company has described cylindrical cell configurations with energy densities and cycle life characteristics that go beyond current commercial EV packs. Whether that chemistry is NMC, NMC-blended, or something further toward higher-nickel cathodes is not publicly confirmed — but the performance claims imply a pack-level design that is not simply assembled from automotive-grade cells.

The FAA certification challenge for batteries in aviation is distinct from automotive. There is no FAA-approved battery certification standard with the same pedigree as DO-160G for environmental conditions or DO-178C for software. FAA Special Conditions documents for eVTOL battery systems require OEMs to demonstrate — and flow to suppliers the obligation to demonstrate — thermal runaway containment, cell-to-cell propagation prevention, and structural integrity across the operational and emergency envelopes. For Joby’s suppliers providing battery modules or cell supply, this creates documentation demands that automotive-grade suppliers are often not structured to meet.

Specifically, battery Tier 1s must produce:

• Design substantiation data linking cell chemistry to module-level performance bounds
• Hazard analysis traceable to aircraft-level safety objectives (typically targeting 10⁻⁹ catastrophic failure probability per flight hour)
• Manufacturing process documentation sufficient for FAA Production Approval Holder (PAH) or supplier delegation under Joby’s own PAH
• Environmental qualification test data to DO-160G, adapted to the thermal and vibration environment of the specific installation location in the airframe

This is not a documentation exercise that most battery manufacturers — even sophisticated ones — have done before. The requirement to integrate cell-level data into aircraft-level safety cases requires either a very capable supplier quality engineering team or heavy involvement from Joby’s own systems engineers, which is a resource that scales badly across a supply base.

Avionics Integrators: The DO-178C/DO-254 Burden

Joby’s avionics architecture includes fly-by-wire flight control, vehicle management computing, sensor fusion for navigation and obstacle detection, and integration with air traffic management systems required for commercial operations. The suppliers contributing to this layer — whether providing DAL A flight control software, DAL B sensor processing, or integration computing hardware — operate in the most process-intensive part of the supply chain.

DO-178C (software) and DO-254 (complex electronic hardware) compliance requires a specific development and verification process: planning documents, requirements traceability matrices, structural coverage analysis, independence requirements for verification. For a DAL A component, the cost to generate the required compliance evidence can be comparable to or exceed the cost to write the software itself. This is well understood in traditional aviation. What is less settled in the eVTOL context is what DAL assignments apply to novel functions — autonomous hover recovery, propulsion system management across twelve motors, degraded-mode operation — that have no direct precedent in Part 23 or Part 25 certified aircraft.

Joby is understood to be working directly with the FAA through its G-1 issue papers to establish the DAL assignments for novel functions. Until those assignments are finalized, suppliers writing software for those functions are in a difficult position: they can begin DO-178C compliant development, but at a DAL level that may be adjusted by regulator agreement, requiring rework of planning and verification artifacts.

This is not a criticism of Joby’s certification strategy — it is the correct approach given that there is no established means of compliance. It is, however, a realistic description of the supplier environment: specification instability at the OEM level propagates downstream as qualification rework risk.

ITAR and the Compressed Supplier Pool

ITAR controls on aviation technology are a structural factor in Joby’s supply chain composition. Flight control software at DAL A, certain propulsion components, and elements of the navigation system fall under ITAR controls that restrict access to foreign nationals and require export licenses for international supplier engagement. For a startup OEM trying to build the most competitive supply chain globally, ITAR is a binding constraint on sourcing flexibility.

The practical effect is that Joby’s pool of qualified, ITAR-compliant suppliers for flight-critical subsystems is concentrated in the U.S. and a limited set of allied nations. For novel components — battery packs with aviation certification heritage, high-performance tilt-rotor motors, avionics computing platforms with DO-254 DAL A pedigree — the intersection of “technically capable,” “ITAR-compliant,” and “willing to engage in the non-recurring engineering demands of a development program” is a small set.

This is where Joby’s Toyota investment relationship and its relationship with other strategic investors has operational significance beyond capital. Access to supply chain development relationships, manufacturing process knowledge, and quality system infrastructure through investor networks can partially offset the constraints of the qualified vendor pool. Whether those relationships translate to certified component supply or only to manufacturing process support is not publicly disclosed.

The Concurrent Engineering Problem

The most structurally difficult challenge in Joby’s supply chain is not any individual technical requirement — it is the concurrent engineering problem inherent in developing novel supplier components in parallel with an aircraft-level design that is itself still being validated.

In a mature commercial aircraft program, supplier SOWs are written against a substantially stable aircraft-level specification. The OEM’s systems engineering team has closed the aircraft design to a level where subsystem requirements — interfaces, performance bounds, failure mode allocations — are relatively stable before major supplier development contracts are placed. This is not achievable on a novel eVTOL program on an aggressive certification schedule.

The result is that Joby’s Tier 1 suppliers are writing FMEAs, safety analyses, and qualification plans against requirements that carry non-trivial probability of revision. Each requirements change triggers not just engineering rework but documentation rework — updated traceability, updated verification plans, sometimes updated test configurations. For suppliers with aviation certification experience, this is a known cost of development programs and is contractually managed through CDRLs and engineering change order processes. For suppliers entering aviation from automotive or defense backgrounds, the cost of this iteration is often underestimated.

Joby’s systems engineering team bears the burden of managing the interface between aircraft-level requirement stability and supplier development pacing. This means maintaining a requirements baseline that is stable enough for suppliers to plan work against, while remaining open enough to incorporate aircraft-level changes driven by ongoing test and certification dialogue with the FAA. It is a genuine engineering management challenge, and the tools used to maintain bidirectional traceability across that interface — from aircraft-level safety objectives to supplier deliverables — directly affect program execution.

What Entry Into Service Actually Requires From Suppliers

As Joby moves toward type certificate and production, the supplier demands shift character. Development-phase suppliers delivering qualification evidence give way to production-phase suppliers required to operate under FAA-approved quality management systems, maintain first article inspection records, and support FAA production inspections. Not all development-phase suppliers are structured or willing to make that transition.

Joby’s production approval path — whether through its own PAH or through delegated supplier approvals — requires each Tier 1 producing a life-limited or flight-critical component to demonstrate production repeatability, not just design adequacy. This is the phase where automotive-heritage suppliers most frequently encounter the gap between their quality systems and FAA requirements. AS9100 compliance is necessary but not sufficient. Suppliers producing flight-critical composites, electrical harnesses, or electronic assemblies must in many cases stand up dedicated quality systems, designee relationships, or DER/DAR engagements to support production approval.

The suppliers that navigate this transition successfully are those who treated certification evidence as a first-class engineering deliverable throughout the development phase — not as a documentation task appended at the end. That discipline, in turn, depends on how well requirements were maintained, traced, and communicated across the OEM-supplier interface from the beginning of the program.

Honest Assessment

Joby’s supply chain is building hardware for which there are no fully established certification precedents, under regulatory requirements that are still being defined, on a schedule driven by market and investor expectations. The Tier 1 suppliers who are succeeding in this environment share several characteristics: they entered with existing aviation certification infrastructure, they invested early in systems engineering capability rather than treating it as overhead, and they built contractual mechanisms to manage requirements instability without allowing it to freeze their development pace.

The suppliers who are struggling — and in any novel aircraft program of this complexity, some are — tend to be those who underestimated the documentation burden relative to the engineering burden, or who treated requirements flow-down as a contract compliance exercise rather than a systems integration tool. The aircraft will eventually fly commercially. The question of which Tier 1s are still attached to the program when it does is being answered now, in engineering review meetings and qualification test results that are not publicly disclosed.