AS9120 vs AS9100: What's the Difference and Why It Matters for Buyers

Two certifications dominate supplier quality paperwork in aerospace distribution: AS9100 and AS9120. They look similar on a certificate, they share most of their DNA, and they are routinely confused — including by people who have been buying parts for years. The difference matters, because each one tells you something specific about what the certified organization does and what its audits actually examined.

Here is the practical distinction: AS9100 is written for organizations that design and manufacture aviation, space, and defense products. AS9120 is written for stockist distributors — companies like Instaparts that buy finished hardware and resell it without changing it. Everything else about the two standards follows from that split.

One Family, Three Siblings

The International Aerospace Quality Group (IAQG) publishes a small family of quality management system standards built on a common chassis: the complete text of ISO 9001, plus additional requirements specific to aviation, space, and defense. The three you will encounter are AS9100 for organizations that design or manufacture, AS9110 for maintenance and repair organizations, and AS9120 for stockist distributors. Certification to any of them is issued by accredited certification bodies after on-site audits, and certified organizations are listed in the IAQG's OASIS database — which means a claimed certification is verifiable, not just a logo on a website.

The current revisions — AS9100 Rev D and AS9120 Rev B — were restructured in 2016 around ISO 9001:2015, so both share the same clause skeleton. What differs is the content bolted onto it.

What AS9100 Covers

AS9100 assumes the certified organization creates product. Its aerospace additions concentrate on the risks of design and production: design and development controls, configuration management, control of work transfers, production process verification, special process control, product safety, and — since Rev D — explicit counterfeit part prevention requirements. When a machine shop or an OEM shows you an AS9100 certificate, the message is: the system that designs, plans, and builds this product has been independently audited against the industry's QMS benchmark.

What AS9120 Covers — and Why It Exists

A distributor does not design bushings and does not machine them. Auditing a stockist against design-and-development clauses would produce a stack of “not applicable” findings and miss the risks that actually live in distribution: losing traceability, mixing lots, mangling documentation, and letting counterfeit or suspect parts into stock.

AS9120 exists to aim the audit at those risks. Relative to AS9100, it removes the design and manufacturing-specific clauses and strengthens the requirements that matter when product passes through a distributor's hands unchanged:

• Traceability. Product must remain identified and traceable to the original manufacturer through receipt, storage, and shipment, with manufacturer documentation retained and passed through to the buyer.
• Lot splitting. When a distributor breaks a manufacturer's lot into smaller sale quantities, controls must preserve each split quantity's link to its parent lot and its documentation.
• Evidence of conformity. Certificates of conformance and supporting documents must be controlled, retained, and furnished so the buyer inherits a complete chain.
• Counterfeit and suspect part prevention. The distributor needs processes to avoid, detect, and control counterfeit and suspected unapproved parts — see our companion article on AS6081 counterfeit controls.
• Record retention. Records — including traceability records — are retained per defined requirements, which customer flow-downs frequently extend.

What Each Certificate Tells a Buyer

Neither certificate certifies a part. This is the most common misreading. AS9100 and AS9120 certify management systems: they tell you the organization's processes were audited, findings were closed, and surveillance audits continue. For a buyer, the practical reading is:

• An AS9100 supplier: the processes that design and build your part are systematically controlled.
• An AS9120 distributor: the processes that receive, store, split, document, and ship your part are systematically controlled — with traceability and counterfeit prevention audited explicitly.

Your purchase order still does the part-level work: it specifies the standard and revision, the traceability you require, and the certificates that must accompany the shipment. And if a supplier cannot tell you which certification they hold — or the certificate has quietly lapsed — that is an answer too.

Flow-Down Requirements, in Plain Terms

“Flow-down” is contract language for a simple chain: your customer imposes requirements on you, and you are obligated to impose the applicable ones on your suppliers, all the way down the tiers. Typical flowed-down requirements include specification revisions, traceability and record retention periods, right of access for audits, counterfeit prevention clauses, and notification requirements for nonconformances or changes.

For a buyer, the practical question is whether your distributor can accept your flow-downs. A distributor operating an AS9120 QMS is structurally built for this: document control, record retention, and traceability processes exist precisely so customer clauses can be honored — and demonstrated when your own auditors come asking. Ask that question before the first order, not during your first audit finding.

Why the Chain of Custody Is the Whole Game

In aerospace, hardware without documentation is not really hardware — it is unusable material with good dimensions. If the paper chain from the original manufacturer breaks anywhere between the mill and your stockroom, you cannot demonstrate conformance, and the part's value collapses regardless of its actual quality.

This is the concrete reason AS9120 matters when you choose a distributor. Every audited control — receiving verification, identification, storage, lot splitting, certificate pass-through — exists to keep that chain intact while product sits on a shelf or gets divided into smaller quantities. Instaparts operates an AS9120 Rev B certified QMS: every order ships with a certificate of conformance and full traceability, backed by AS6081-based counterfeit prevention controls. You can read more about how we work on our about page, or go straight to the parts catalog.