The short answer
ISO 9001 is the general quality-management baseline. AS9100 builds on that baseline with aerospace-specific controls around risk, traceability, configuration, and process discipline. If you are buying general industrial parts, ISO 9001 may be enough. If the part is aerospace or tied to aerospace flowdowns, AS9100 is usually the stronger and more relevant requirement.
What ISO 9001 actually tells you
ISO 9001 says the supplier operates a documented quality-management system and is expected to control processes, records, corrective action, and continuous improvement. That matters. It is the standard floor for many industrial buying organizations because it signals discipline without forcing sector-specific overhead.
But ISO 9001 does not tell you the supplier is set up for aerospace traceability, first article expectations, configuration rigor, or customer flowdowns. A good ISO 9001 shop can still be the wrong supplier for a flight-critical part.
What AS9100 adds
AS9100 keeps the ISO 9001 core and adds aerospace-specific expectations. That usually means tighter attention to product safety, counterfeit prevention, risk management, configuration control, traceability, and how changes are handled across the route. For aerospace procurement, those additions matter because the failure cost is very different.
AS9100 does not automatically mean the shop is perfect. It does mean the system is built for a more demanding supply-chain environment than a generic industrial QMS.
When buyers over-specify
A lot of buyers ask for AS9100 because it sounds safer, even when the part is a non-flight industrial bracket or a simple service spare with no aerospace flowdown. That can shrink the supplier pool, raise price, and add zero practical value.
The smarter move is to match the certification requirement to the actual program risk. Use the standard as a screening tool, not as decoration.
What to ask besides the certificate
Certification is only the starting filter. Buyers still need to check whether the supplier has real experience with the part family, material, tolerances, and documentation package involved. A certified shop that rarely makes parts like yours is still a risk.
Also ask whether outside processes, FAI, traceability, and customer approvals are controlled inside the same system. That is where the real execution lives. Related reading: First article inspection: what it is, what it covers, and when to require it and ITAR compliance for machined parts: what procurement teams need to know.
Comparison table where relevant
| Certification | Best fit | Buyer watchout |
|---|---|---|
| ISO 9001 | General industrial machining | Does not equal aerospace discipline |
| AS9100 | Aerospace and defense supply chains | Still validate part-family fit |
| Either one | Screening tool only | Not a substitute for technical review |
| No relevant certification | Low-risk internal buys only | Weak signal for controlled programs |
How to specify this in your RFQ
State the exact certification requirement in the RFQ and say whether proof is needed at quote stage or before award. If the part is tied to aerospace flowdowns, say that clearly. If ISO 9001 is enough, do not quietly imply AS9100-level control and expect it for free.
Have a part that needs quoting? Email your drawings to rfq@precisionmachining.co - we return a competitive quote within 24 hours. Phone: +1 312-579-0808.