FAA Regulatory Parts Explained for AAM Operators

There are more solutions than obstacles. Nicolas Zart

I wanted to write an article on the various Federal Aviation Agency (FAA) of the United State’s Part system since it can get confusing. How do they relate to advanced air mobility (AAM), and what do they mean for the nascent industry?

FAA Regulatory Parts Explained: What Each One Means for AAM

The Federal Aviation Administration (FAA) governs U.S. aviation through Title 14 of the Code of Federal Regulations. This is the body of rules organized into numbered “Parts,” each covering a distinct domain of aviation safety, certification, and operations. For most of commercial aviation’s history, those Parts operated in relatively stable roles. However, Advanced Air Mobility (AAM) introduced new territories and is stress-testing how they all come together in a safe and coherent way.

Understanding which Parts govern which aspects of AAM — and where the regulatory gaps remain — is foundational knowledge for anyone interested in this sector.

The Certification Backbone: Part 21 and Part 23

Part 21 is where every aircraft’s journey begins. This is the certification procedure for all aeronautical products. It includes type certificates (TC), supplemental type certificates (STC), and production certificates (PC). Every eVTOL that enters commercial service in the U.S. will do so through Part 21. It is the gateway, not the standard.

The airworthiness requirements lives primarily in Part 23 for eVTOLs. Part 23 was originally written for conventional fixed-wing aircraft in the normal, utility, acrobatic, and commuter categories. However, 2017 amendments shifted it to a performance-based framework. This gave the FAA more flexibility in applying it to newer configurations. Since then, the FAA has designated eVTOLs as “powered-lift” aircraft and is currently working through pathways — including Special Federal Aviation Regulations (SFARs) and Part 23 amendments — to create a durable certification framework for the category.

Parts 27 and 29 cover rotorcraft — normal category (under 7,000 lbs) and transport category respectively. For eVTOLs with predominantly rotorcraft-like configurations, these Parts may provide relevant precedent, though powered-lift aircraft are not rotorcraft by definition.

Part 33 governs aircraft engine certification and Part 35 covers propellers. These last two are both relevant as electric propulsion systems and distributed electric propulsion (DEP) require the FAA to apply or adapt existing standards to configurations those Parts were not originally written to address.

Operations: Parts 91 and 135

Once an aircraft is certified, Part 91 governs how it flies. Part 91 covers general operating and flight rules for all aircraft as the baseline operational framework. Part 135 governs commuter and on-demand operations: air taxis, charter operations, and similar services with up to 30 seats. The commercial AAM model — on-demand urban air taxi service — maps most directly onto Part 135. This means that AAM operators will need both aircraft certification (Part 21/23) and operator certification (Part 135) before generating commercial revenue. This explains why some OEMs already have either or one of those.

Part 91K governs fractional ownership programs, which may become relevant as AAM fleet models evolve beyond direct operator ownership.

Maintenance: Part 145

Part 145 governs approved repair stations and maintenance organizations, maintenance, repairs, and overhaul (MRO). Any entity performing maintenance on certificated AAM aircraft for commercial operations will need to meet Part 145 requirements. This creates both a compliance obligation and a business opportunity — the AAM maintenance ecosystem is nascent, and the companies that build Part 145-compliant infrastructure for electric propulsion systems and novel airframe configurations will be positioned as critical supply chain nodes.

Infrastructure: Parts 157 and the 150 Series

The physical infrastructure layer — vertiports/multiports — does not have a dedicated FAA Part. Part 157 governs notice of construction or alteration of airports, which provides a partial framework. Instead, the FAA relies on Advisory Circulars (ACs) in the 150 series to address vertiport/multiport design and operations. These ACs carry less regulatory weight than Parts but provide guidance that operators and developers are using to structure their projects in advance of formal rulemaking.

It is also important to state that International Civil Aviation Organization (ICAO) operates as a standard-setting body under the United Nations, publishing requirements through what it calls Standards and Recommended Practices (SARPs) Spread out across 19 technical Annexes, they cover everything from aerodrome design to safety management systems. Standards and recommended practices, means the ICAO itself has no enforcement authority. Its 193 member states are obligated to implement ICAO Standards into their own national regulations — or formally notify ICAO of any differences under Article 38 of the Chicago Convention. Recommended Practices, meanwhile, carry no obligation at all — member states are simply encouraged to adopt them where practicable.

ICAO compliance frameworks flow through each country’s national aviation authority — the FAA in the United States, EASA across the European Union, ANAC in Brazil, and so on. Authorities may adopt ICAO standards verbatim, adapt them, or formally register differences. For emerging infrastructure like vertiports and multiports, where ICAO guidance is still evolving and no binding national regulations yet fully address the asset class. Operators and developers are largely working from a patchwork of advisory material, national authority guidance circulars, and their own interpretation of how existing aerodrome standards translate to new operational environments. The framework exists — but there are no obligations as they remain largely discretionary.

The absence of a dedicated vertiport regulatory Part with the FAA is significant. It never happened with the helicopter industry and its heliport counterpart. It reflects where the infrastructure layer sits in the FAA’s regulatory development timeline — important, acknowledged, but not yet fully addressed if ever.

The Certification Roadmap and Understanding Press releases

Readers here will understand my concern with over-enthusiastic press releases muddling the convoluted road map to aircraft certification. The following is a breakdown of an aircraft certification in the USA with the FAA.

The FAA aircraft certification framework is a layered system of approvals, each serving a distinct purpose. Here is a clear, structured explanation:

The Core Concept

FAA certification is not a single process — it is a family of certificates that together confirm a design that is safe, where each unit produced matches that design, and that the aircraft in service remains airworthy. It asks three separate questions: Is the design safe? Is this specific aircraft built correctly? Is it still safe in operation?

The Major Certificate Types

1. Type Certificate (TC)

The TC is the foundational approval — it certifies that an aircraft design meets FAA airworthiness standards. Nothing else is possible without it. This is where Joby Aviation is, clearly the furthest along compared to its competition.

The TC process has five formal phases according to the FAA:

1. Pre-Application — Manufacturer engages the FAA, establishes a Certification Project Team (CPT), and defines the certification basis (which specific regulations apply)
2. Formal Application — Manufacturer submits the application package; FAA reviews and accepts it; certification basis is formally established
3. Design Assessment — FAA evaluates all engineering data, drawings, analyses, and proposed compliance methods; ground and structural tests are conducted
4. Performance Assessment — Flight testing begins; manufacturer demonstrates the aircraft performs as claimed under all conditions; FAA witnesses critical tests
5. Airworthiness Determination & TC Issuance — All data is reviewed for closure; if everything passes, the TC is issued

For novel designs like eVTOL aircraft, the FAA often establishes a special certification basis through Issue Papers and Special Conditions, since existing regulations were not written for these configurations.

2. Production Certificate (PC)

Once a TC exists, the PC certifies that a manufacturer’s production system can repeatedly build aircraft that conform to the approved type design. It covers facilities, quality systems, supplier oversight, and conformity inspection processes. Every aircraft rolling off the line must match the TC — the PC is how the FAA ensures that happens at scale.

3. Airworthiness Certificate (AC)

Issued to each individual aircraft, confirming that specific serial number conforms to its type design and is safe to fly. There are two categories according to the FAA:

• Standard Airworthiness Certificate — for production aircraft that fully meet TC and PC requirements; the certificate a passenger airline aircraft carries
• Special Airworthiness Certificate — covers experimental, research, and limited-category aircraft; critical for eVTOL developers in the testing phase before full TCfaa

4. Supplemental Type Certificate (STC)

An STC approves a modification to an already type-certified aircraft. When a company wants to change something on an existing certified design — a new avionics suite, an electric propulsion conversion, a structural modification — they cannot simply do it. They must prove the modification is safe and does not negatively affect the original design.

The STC process mirrors the TC process in miniature:

1. Applicant applies and holds familiarization meetings with FAA
2. FAA develops a Certification Program Plan and establishes the certification basis
3. Applicant submits engineering data and analysis
4. FAA design evaluation and conformity inspections
5. Ground tests and flight tests, witnessed by FAA or designated representatives (DER/DAR)
6. FAA issues Type Inspection Authorization (TIA) for test flights
7. Functional and reliability testing
8. Final Type Certification Board meeting
9. STC issued

5. Parts Manufacturer Approval (PMA)

A PMA authorizes a company other than the original manufacturer to produce replacement or modification parts for a certified aircraft. Relevant for the AAM supply chain — any company making components for a certified eVTOL that is not the original TC holder needs a PMA.

6. Technical Standard Order (TSO)

A TSO is an FAA minimum performance standard for specific avionics and equipment — transponders, autopilots, navigation systems. A TSO authorization certifies that a specific piece of equipment meets those standards. It is not an aircraft-level approval but an equipment-level one.

The Full Certification Map

To recap, here’s a road map of the full certification for an aircraft.

The AAM Context

For eVTOL companies, the path typically runs: Special Airworthiness Certificate (Experimental) → flight testing → TC → PC → Standard Airworthiness Certificates for each production aircraft.

What EASA Does Differently

European operators face a parallel but distinct regulatory structure. EASA uses its own Part 21 for design and production approvals, CS-23 and CS-27 as certification specifications for fixed-wing and rotorcraft respectively, and Part-M and Part-145 for continuing airworthiness and maintenance. For eVTOLs specifically, EASA issued Special Condition VTOL (SC-VTOL) in 2019 — the closest equivalent to a dedicated eVTOL certification standard currently in force globally. SC-VTOL is evolving toward a full CS-VTOL standard as the data from early certifications accumulates.

Bilateral agreements between the FAA and EASA — including the Technical Implementation Procedures (TIP) — allow type certificates issued under one authority to be validated by the other, which is essential for OEMs seeking both U.S. and European market access.

The Regulatory Horizon

No entirely new FAA Part specific to AAM has been proposed. The regulatory development path runs through amendments and adaptations of existing Parts, with powered-lift category integration into Part 23 as the central near-term deliverable. The FAA’s AAM Implementation Plan targets 2028 as the horizon for initial commercial operations under an adapted regulatory framework.

For operators, the practical implication is that the regulatory environment is functional but incomplete. Certification is achievable. The pathway is defined, if demanding. The infrastructure regulatory framework is still forming. And the operational framework — particularly for scaled, multiport commercial operations — will require continued engagement with the FAA as the rulebook catches up to the aircraft.

The Parts are the foundation. The industry is being built on top of them in real time.