Every aerospace part starts with a first article. Whether it's a single prototype or the first piece of a 500-unit production run, your machining supplier needs to prove the part is built right before anyone commits to volume. That's what first article inspection does — and in aerospace and defense, it's not optional. It's a contractual requirement under AS9100D, and the document that proves compliance is the AS9102 First Article Inspection Report.

This guide covers what FAI means for aerospace buyers and engineers sourcing CNC-machined parts: when it's triggered, what the AS9102 forms actually require, why parts get rejected on first article, and how to plan your procurement timeline so FAI doesn't become a schedule surprise.

What Is First Article Inspection?

First article inspection is the systematic verification that a manufactured part meets all drawing requirements before it enters normal production. The "first article" is literally the first part off the tool — a prototype, pre-production, or initial production piece that gets measured against the engineering drawing and documented in a formal report.

In aerospace and defense, FAI is governed by AS9102, "First Article Inspection Requirements." AS9102 is a mandatory part of AS9100D-certified quality systems, which means any prime contractor or OEM requiring AS9100D from their suppliers will require AS9102-compliant first article inspection reports. If you're buying machined parts for an aerospace program, FAI is almost certainly a flow-down requirement in your purchase order.

The FAI process does three things:

For a CNC machining supplier, FAI is a significant process investment. A complete AS9102 package on a complex aerospace part takes 8–20 hours of inspection labor alone, not counting the setup and documentation work. Understanding what's required lets you set realistic lead times and avoid the quote-then-fight about "why is FAI so expensive?"

AS9102 Forms 1, 2, and 3: What Each One Does

AS9102 defines a three-form inspection package. Each form serves a distinct purpose — together they give the buying organization everything they need to verify the part and make a sourcing decision.

Form What It Covers Key Content
Form 1 — Part Number Identifier Part identity, build state, and inspection scope Part number, revision, serial number, build quantity, part description, drawing number and revision, manufacturing location, FAI date, inspector ID, supplier cage code
Form 2 — Characteristics Accountability All dimensional measurements, one per row Characteristic number (matches drawing), dimension description, nominal value, measured value, actual deviation, tolerance (+/-), accept/reject status, measurement equipment ID, measurement method (CMM, hand gauge, etc.)
Form 3 — SupplementalPartData Process data, material certs, and supporting evidence Material heat/lot numbers and certifications, special process records (heat treat, anodize, NDT), tooling and fixture IDs used, as-built CAD model or printout, nonconformance reports if applicable, CMM program reference

All three forms are required for a complete AS9102 FAI package. A Form 1 and Form 2 with no Form 3 is incomplete — your quality department will reject it on material certs alone. The three forms are designed to be read together: Form 1 identifies the part, Form 2 proves it measured correctly, and Form 3 documents that the materials and processes behind those dimensions were compliant.

A note on AS9102 revision

The current revision of AS9102 is Rev B. If you're seeing FAI packages with Rev A forms, that supplier's quality system may be outdated or using legacy documentation. Ask to confirm their AS9102 revision matches your program requirements — and check that their AS9100D certificate references AS9102 Rev B.

When Is FAI Triggered?

FAI is required for new parts, but the triggers extend beyond "first time we order this part." Common situations that trigger FAI:

The practical implication for procurement: don't assume FAI only happens at program award. If your program has a drawing revision coming, a supplier change, or a material source change in the pipeline, account for FAI time and cost. The quote you got at program start was probably calculated assuming a single FAI at program launch — not a recurring event.

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The Machinist's Perspective: What Actually Causes FAI Failures

From the shop floor, FAI failures almost always come down to one of four categories. Understanding these helps you write better RFQs and avoid surprises.

1. Drawing/Dimension Ambiguity

When a dimension is toleranced ambiguously, the machinist builds to their interpretation — which may not match what the inspector or the engineering team expected. This shows up most often with:

The fix isn't on the shop — it's in the drawing review before the RFQ goes out. If your engineering team is sending ambiguous prints, you're going to get FAI rejects regardless of how capable the machine shop is. A good supplier will flag ambiguity during quote review. A machinist who doesn't flag it and then produces to their own interpretation is doing you a disservice.

2. Process Capability Issues on Tight Features

Certain features — thin webs, deep bores, tight-hold tapers, mirror-finish surfaces — have process capability limits even when the drawing allows them. A ±0.0005" perpendicularity on a thin wall machined in a 3-jaw chuck on a part with asymmetric residual stress isn't a measurement problem. It's a fixturing problem, and sometimes there's no fixturing solution that makes the geometry achievable within that tolerance without a production-grade process redesign.

The machinist's job is to build the part. If the part can't be built to the drawing with available fixturing and process, the machinist should push back before production — not during FAI.

3. Wrong Material or Heat Treat State

FAI fails on material cert mismatch more often than most buyers expect. Common scenarios:

For machined aerospace parts, traceable material certs from the raw bar stock through machining to the finished part are non-negotiable. The Form 3 documentation requirement exists precisely to catch material chain-of-custody breaks.

4. Inspection Method Doesn't Match the Dimension

A hand micrometer reads differently than a CMM on an aluminum part that expands 0.002" per inch when it goes from ambient to the CMM's 68°F reference temperature. A bore gauge reads bore size but not geometric error. If the inspection method used on Form 2 doesn't capture the actual characteristic being called out — and doesn't match what was used during the FAI acceptance decision — you have a documentation problem.

AS9102 requires documented measurement methods and equipment IDs for a reason. If a dimension is called out as a profile with a GD&T callout, the measurement method on Form 2 needs to be a CMM program — not a hand indicator sweep.

CNC-Specific FAI Considerations

CNC-machined aerospace parts have specific FAI requirements that often differ from cast, forged, or sheet metal parts. Here's what aerospace buyers and engineers should know about the inspection process for CNC work.

CMM Inspection Is the Baseline, Not the Exception

For CNC-machined aerospace parts, coordinate measuring machine (CMM) inspection is effectively required for any characteristic at ±0.001" or tighter. Hand gauges (micrometers, calipers, bore gauges) don't have the repeatability to reliably demonstrate that tight-tolerance features are within drawing requirements — and more importantly, CMM inspection produces a measurement record that can be audited and referenced on Form 2.

At a shop with AS9100D certification, CMM capability is a baseline requirement. If a machining supplier is quoting tight-tolerance aerospace work without offering CMM inspection, that's a quality system gap — not just a capability gap.

Datum and Setup Documentation

Form 2 requires each characteristic to be traceable to a specific datum reference frame. For CNC-machined parts, this means the setup — which face is primary datum A, which edge is datum B, what location is datum C — must be documented on the FAI forms. If the part was flipped in a vise, re-fixtured after heat treat, or machined in multiple operations, each operation's datum reference must be identifiable.

A common FAI failure: a part machined in two operations, datum-shifted between operations, with no documented setup reference for Operation 2's dimensions. The inspector measures the dimensions correctly, but the documentation doesn't show how those dimensions relate to the as-delivered part's datum frame.

Program and Machine Verification

When a part is programmed on one machine and run on another — or when a program is revised between FAI and production — the geometric outcome can differ. This is especially true for 5-axis parts with complex toolpaths and for features that depend on machine thermal compensation or spindle runout.

AS9102 doesn't require machine-specific verification for every part, but AS9100D requires documented process control. A shop that runs FAI on Machine A and production on Machine B needs to have a documented basis for why those machines are equivalent for the features in question. Spindle speed variation, axis repeatability differences, and thermal drift profiles all affect this determination.

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Planning Lead Time for FAI Work

FAI adds significant time to a first-run order. Here's how to think about the timeline from a procurement perspective.

Day 0 — Part receipt and job planning
Shop receives drawing, assigns job, reviews dimensions vs. capability, selects machines, designs fixtures. 1–3 days depending on complexity and queue.
Days 1–5 — CNC machining
Roughing, semi-finishing, heat treatment (if required), finishing. Titanium and Inconel parts may require multiple heat treat cycles. 3–10 days for a complex aerospace part.
Day 5–7 — CMM inspection and FAI documentation
Full CMM inspection of all Form 2 characteristics, completion of Forms 1, 2, and 3, material certs pulled, inspection records reviewed. 2–4 days for complex parts, can be same-day for simpler geometry.
Day 6–8 — Internal QA review and customer package delivery
QA engineer reviews FAI package for completeness. Package delivered to customer. Customer has a review window before production release — this varies by program.

Realistic total: 10–20 business days from job release to completed FAI package for a moderately complex aerospace part. Complex multi-operation parts or parts requiring exotic material procurement can run 4–6 weeks. Your RFQ timeline should reflect this — especially on new programs where FAI is part of source qualification, not just a delivery formality.

Lead time tip: FAI-ready means ready at quote

If you need FAI on a part, mention it at the quote stage — not after the PO is issued. A machinist quoting against a tight timeline who finds out at job start that FAI is required will quote their standard machining time and then add FAI as an afterthought, creating billing disputes and schedule pressure. Quote it up front and build the timeline into your procurement schedule.

Most Common FAI Rejection Reasons

These are the failure modes we see most often on aerospace CNC FAI packages — whether we're the supplier doing the inspection or reviewing a customer's supplied FAI data.

Rejection Reason What It Looks Like How to Prevent It
Missing material certifications Form 3 has no heat lot trace, or cert is from wrong material spec Confirm material cert source at quote; require certs with raw material delivery
Incomplete Form 3 Special process records (heat treat, NDT) missing or from unapproved processors Review approved processor list before award; add NADCAP processors if required
Wrong measurement method on Form 2 Hand gauge used for a GD&T profile or position callout requiring CMM Verify CMM capability at qualification; review Form 2 measurement methods before acceptance
Datum reference not documented Form 2 shows measured values with no datum frame reference for some characteristics Require full GD&T datum frame documentation at quote; flag missing datums before machining
Out-of-tolerance dimension with no NCR Dimension on Form 2 shows out-of-tolerance value but no nonconformance report is attached All out-of-tolerances require documented disposition (use-as-is, repair, scrap)
Wrong revision of drawing Part built to old revision; FAI package references new revision but part doesn't reflect changes Confirm drawing revision at job release; lock revision on PO before machining begins

Working With Your Supplier on FAI

FAI is a partnership. A good supplier will engage during the quote phase to identify drawing ambiguities, flag process risks, and estimate realistic inspection time. Here's what that relationship looks like on a well-run aerospace program.

Quote review and pre-FAI planning

Before you award the job, your supplier should review the drawing against the RFQ and identify:

If your supplier quotes the machining without mentioning FAI and then presents a $3,000 FAI invoice on delivery, that's a quoting problem — not an inspection problem.

FAI package review and approval

When your supplier delivers the AS9102 package, your quality team should review it against the drawing — not just accept it as complete. The review checklist:

For detailed coverage of DFARS compliance requirements, including specialty metals and NIST 800-171 cybersecurity flow-downs that often accompany FAI requirements, see our DFARS compliance guide for machine shops. For ITAR requirements at the shop floor level, see our ITAR machining guide.

FAI Requirements Checklist for Aerospace Buyers

Use this before issuing your next RFQ for CNC-machined aerospace parts:

For deeper coverage of aerospace tolerances, AS9100D requirements, and CMM inspection standards, see our aerospace CNC tolerances guide. For the full range of defense machining requirements including DFARS specialty metals and ITAR compliance, see CNC Machining for Defense.

Common FAI Questions

Can a supplier skip FAI if the first article looks correct?

No. FAI is a documented process requirement under AS9100D, not a quality judgment call. The documentation — Forms 1, 2, and 3 — is what the prime contractor or OEM requires. An uninspected part that "looks right" doesn't have a paper trail, and it cannot be production-released on an AS9100D-controlled program.

Do all production parts require FAI, or just the first piece?

Standard AS9102 FAI is required once per "build event" — typically the initial production run. Subsequent production runs don't require full FAI unless a re-FAI trigger is met (revision change, supplier change, process change). However, some programs require first piece inspection on every lot or batch — check your program's specific flow-down requirements.

What's the difference between FAI and PPAP?

PPAP (Production Part Approval Process) is an automotive industry standard from AIAG (Automotive Industry Action Group). FAI under AS9102 is the aerospace equivalent. They serve similar purposes — prove the supplier can produce the part consistently — but the documentation requirements, forms, and standards are specific to each industry. Don't ask for PPAP on an aerospace program; ask for AS9102. The form structure and content requirements are different.

How long is a FAI package valid?

There's no fixed expiration period in AS9102. Validity depends on your program's specific requirements and whether any re-FAI triggers have been met. Some programs define a maximum interval (e.g., FAI valid for 24 months unless a trigger event occurs). Check your prime's quality assurance requirements for the specific validity window on your program.

Can we use a supplier's existing FAI from a previous program to reduce lead time on a new order?

Possibly, if the part number, revision, and material are identical and no re-FAI triggers have been met. However, the existing FAI must be reviewed against your current program requirements, and the supplier must confirm no process changes have occurred since the original FAI. For programs requiring PPAP-level traceability, the answer is almost always "new FAI required" — confirm with your quality team.

Summary: What Aerospace Buyers Need to Know About FAI

First article inspection under AS9102 is the standard proof mechanism for aerospace CNC-machined parts. It's not a quality control step — it's a contractual documentation requirement that proves your supplier can produce the part to drawing before you commit to volume.

The three forms do different jobs: Form 1 identifies the part, Form 2 measures every critical and semi-critical dimension and records the results, and Form 3 backs up the dimensional data with traceable material certs and special process records. All three are required.

FAI lead time adds 2–5 weeks to a first-run machining order depending on part complexity. Price it into the program from day one. If FAI isn't on the quote, add it before the PO goes out.

The most common FAI failures — missing material certs, wrong measurement methods, incomplete Form 3 — are avoidable with clear requirements at the RFQ stage and an engaged supplier who flags drawing ambiguity during quote review. The supplier who says "we'll figure it out" at the quote stage will say "this is as-built" during FAI — which is a schedule disaster for aerospace programs.

Apex Manufacturing performs AS9100D-compliant FAI on every part that requires it. We use Hexagon CMM inspection for all tight-tolerance characteristics, AS9102 Rev B forms, and traceable material certs from source to delivery. Send your drawings with FAI requirements and we'll confirm lead time and pricing before you commit.