If you've spent time reviewing machining-supplier qualification packages, you've seen ISO 9001 and AS9100D listed next to each other like they're versions of the same thing. They're not. They're two different quality management standards, with two very different scopes — and the difference matters enormously the moment you're sourcing for an aerospace, defense, or regulated industrial program.
This is a procurement-side explainer. Not a quality-manager deep-dive — a buyer's guide. What each cert actually requires, what it does and doesn't tell you, and how to size up a supplier from the outside.
ISO 9001:2015 — the foundation
ISO 9001 is the international standard for quality management systems (QMS). It's industry-neutral and applies to any organization that produces a product or service. The 2015 revision shifted the standard toward risk-based thinking — meaning suppliers must identify risks to product quality and customer satisfaction, and document how they manage them.
What ISO 9001 requires, in practical terms:
- Documented procedures for every process that affects product quality (machining, inspection, shipping, complaint handling).
- Measurable quality objectives, reviewed by management quarterly.
- Records: who did what, when, with what equipment, at what calibration state.
- Corrective action when something goes wrong — root cause, not symptom.
- Annual surveillance audit, three-year recertification by a registered body.
ISO 9001 is the baseline most procurement organizations require before sending the first RFQ. It tells you the supplier runs documented, repeatable processes — not somebody's personal craft style. It does not tell you anything about how they handle flight-critical work, counterfeit parts, configuration management, or supplier qualification in a high-stakes supply chain.
AS9100D — ISO 9001 plus aerospace
AS9100D Rev D is the aerospace industry's quality management standard. It is built directly on top of ISO 9001:2015 — every ISO 9001 requirement is in AS9100D — but adds about 100 aerospace-specific requirements that ISO 9001 doesn't cover. The biggest ones:
Risk management for product safety. AS9100D requires a documented risk assessment for every process that could affect product safety, not just product quality. The bar is higher because aerospace parts kill people when they fail.
Configuration management. Every revision of every part has to be tracked through the entire lifecycle — drawing rev, fixture rev, program rev, inspection routine rev. If the customer changes a tolerance in Rev D, the supplier has to show that no Rev C parts shipped after the change date.
Counterfeit-part prevention. Documented controls for raw material sourcing. Material certs traveling with every shipment. Subtier suppliers vetted for counterfeit risk. Domestic-only sourcing for certain aerospace programs.
First Article Inspection per AS9102. Forms 1, 2, and 3 generated against the balloned drawing, with every dimensional and material requirement verified before production runs start. For procurement: when you see "AS9102 FAI on file" in a supplier's package, that's AS9100D speaking.
Special process control. Heat treat, welding, finishing — when these are outside-processed (subcontracted), AS9100D requires the supplier to own the subtier's qualification, not just buy the certificate of conformance.
The audit cadence is the same as ISO 9001 (annual surveillance, three-year recert), but the audit itself is more aggressive. AS9100D auditors come from the aerospace industry; they know what to look for.
Why aerospace primes don't accept ISO 9001 alone
Tier-1 aerospace primes — Boeing, Lockheed, RTX, GE Aerospace — won't put an ISO-9001-only supplier on a flight-critical program. Reasons:
- ISO 9001 doesn't require First Article Inspection. Without AS9102 FAI, the prime can't prove to the FAA that the supplier validated the print before production.
- ISO 9001 doesn't require configuration management. Without it, a supplier could legally ship Rev C parts after a Rev D change without detecting the drift.
- ISO 9001 doesn't require counterfeit-part controls. In the post-2010 era of counterfeit electronics + counterfeit fasteners showing up in mil-spec applications, this is non-negotiable.
If you're sourcing for anything that flies, both certs together is the answer — and AS9100D implicitly includes ISO 9001 in scope.
What this means for your RFQ
Three practical takeaways:
1. Don't list ISO 9001 as a requirement when you actually need AS9100D. Procurement language matters. "ISO 9001 or equivalent" sends ISO-9001-only suppliers into the qualification pool — suppliers who genuinely cannot do flight work. Be specific about what you need.
2. Check the cert scope, not just the cert. An AS9100D certificate has a scope statement that lists which processes are covered (machining, fabrication, welding, etc.). If a supplier is AS9100D-certified for milling but their welding shop is ISO 9001 only, the welding on your part isn't aerospace-grade no matter how many certificates they wave around. Ask for the full cert PDF, not just the registration number.
3. Look at the audit body. Both ISO 9001 and AS9100D have to be audited by an accredited registrar (in the US: ANAB-accredited). For AS9100D, the registrar also has to be aerospace-qualified. If a supplier's cert was issued by an obscure or non-accredited body, the cert is essentially worthless to your prime — they won't accept it for a downstream audit.
How K+G handles this
K+G runs every job through an AS9100D-aligned quality system whether the customer requires it or not. The discipline pays off across non-aerospace work too — tighter configuration control means fewer mis-shipped revs, fewer field failures, fewer customer complaints. For aerospace customers specifically, AS9102 First Article Inspection is auto-generated by the K+G Ai ERP — Form 1, 2, and 3 produced from the balloned drawing in 14 minutes instead of the 11-hour-per-shipment paperwork lift other shops chase.
If you're qualifying suppliers for an aerospace or defense program and want a no-handwaving conversation about cert scope, traceability, and what AS9100D actually does on the floor, drop us a line. We'll send you the full cert package and a real engineer to walk through it.