First Article Inspection (FAI)

First article inspection (FAI) is the formal, documented verification that a manufacturing process can produce an aerospace part that fully meets the engineering definition—before the supplier is allowed to proceed into routine production. In practical terms, FAI is where design intent, manufacturing planning, inspection planning, and the complete traceability record are proven to align. For defense and aerospace programs, FAI is less about “checking one part” and more about demonstrating a controlled, repeatable, auditable workflow under requirements such as AS9100, customer quality clauses, and (where applicable) ITAR and DFARS flow-downs.

Modern aerospace supply chains increasingly blend additive manufacturing (AM) (e.g., powder bed fusion (PBF), DMLS/SLM) with post-processing such as HIP, heat treat, 5-axis CNC machining, surface finishing, and NDE (CT scanning, dye penetrant, etc.). Each additional operation introduces potential variation and additional records that must be represented in the FAI package. Done well, FAI reduces downstream escapes, accelerates approval for follow-on lots, and protects both buyer and supplier when revisions, source changes, or capacity ramps occur.

This article breaks down when FAI is required, what an aerospace-ready report typically includes, how balloon drawings and characteristics are managed, why FAIs fail, how to handle revisions without restarting from scratch, and how buyers and suppliers should structure a practical workflow that stands up to audits.

When FAI is required

FAI is generally required on the first production part manufactured from a new or changed process, and again whenever changes could affect form, fit, function, safety, or interchangeability. Many aerospace organizations follow the structure commonly associated with AS9102-style practices (even when a customer uses their own forms). Regardless of the exact template, the triggering logic is similar.

Typical triggers include:

1) New part / first-time build. The first time a supplier produces a part number to a released drawing and purchase order requirements, including defined special processes and inspection methods.

2) Engineering revision that affects requirements. Any drawing or model change that modifies dimensions, GD&T, notes, material, finish, NDE, or acceptance criteria normally requires at least a partial FAI on affected characteristics. A revision to a requirement note (e.g., a new surface finish, coating thickness range, or added NDE) often triggers more than teams expect.

3) Manufacturing process change. Changes in process route or key parameters such as:• Transition from subtractive to hybrid (e.g., PBF near-net + CNC finish)• New machine tool or PBF system, new build layout strategy, or new scan strategy• New build orientation or support strategy that affects distortion, surface, or internal features• Different HIP cycle, heat treat, or aging schedule• New cutting tools/fixturing, revised CNC program, or new 5-axis setup sequence• Change in post-processing vendors, NADCAP-approved source, or special process method

4) Change in manufacturing location or supplier. Moving production to another facility, adding a second source, or outsourcing a critical operation can trigger FAI because controls, equipment, and competence may differ even if the drawing is unchanged.

5) Lapse in production or loss of process control. If production is stopped for a defined period (common thresholds range from months to a year depending on customer), or if a significant quality escape occurs, a “restart” FAI may be required to re-validate the process.

6) Material or raw stock change that can influence performance. Examples include switching powder supplier/lot for PBF, changing billet forging source, or altering powder size distribution or chemistry limits that influence mechanical properties, porosity, or machinability. Even with identical nominal alloy (e.g., Ti-6Al-4V), the supply chain control and lot traceability may force FAI re-validation.

Procurement note: FAI should be explicitly addressed during RFQ and PO review. If the buyer expects a full FAI, partial FAI, or “delta FAI” after changes, state that up front. For suppliers, clarify whether the customer requires specific forms, characteristic numbering conventions, or additional evidence (e.g., CT scan report for internal lattice verification) beyond standard practice.

Typical report contents

Aerospace FAIs are more than dimensional reports. A procurement-ready FAI package typically combines three categories of evidence: product definition verification (drawing/model requirements), process verification (the route actually used), and traceability/compliance (materials, special processes, and contractual clauses).

Common FAI package elements include:

Part accountability and configuration control
• Part number, name, revision level, and serial/lot identifiers
• Drawing/model identification and any approved deviations/waivers used for the build
• Purchase order, line item, and contract clause references (including flowed-down quality requirements)

Manufacturing route (as-built plan)
• Operation sequence with work order/router steps and sign-offs
• Equipment used (CMM ID, CNC machine ID, PBF machine ID, furnace ID) and relevant calibration status
• Special processes with source identification and certifications (e.g., NADCAP where applicable)

Material traceability and compliance
• Heat/lot traceability for raw material (bar/plate/forging) or powder lot traceability for AM
• Material certifications and test reports as required by the drawing/specification
• Certificates of conformance (CoC) that tie the delivered part to controlled processes and approved sources
• DFARS/Buy American/traceability clauses when applicable (e.g., domestic melt/source requirements), documented in the compliance pack

Dimensional and GD&T verification
• Ballooned drawing with all characteristics identified and cross-referenced to inspection results
• Measurement methods (hand tools, height gage, CMM, optical scanning) and measurement uncertainty considerations for tight tolerances
• Datum scheme verification and setup description (critical for multi-setup 5-axis parts)

Functional, visual, and feature verification
• Surface finish readings where required (Ra/Rz) and notes about measurement direction/trace length
• Thread verification (gaging, pitch diameter where required), helicoils/inserts, and locking feature checks
• Assembly interface checks or go/no-go gaging for mating features when specified

Special processes, heat treat, and post-processing evidence
• HIP charts (time/temperature/pressure) for HIP or PM-HIP builds, including lot/charge traceability
• Heat treat charts and quench/atmosphere information as required by specification
• Plating/coating records, thickness measurements, masking evidence, and bake-outs (e.g., hydrogen embrittlement relief where applicable)

NDE and inspection records
• NDE method reports (e.g., fluorescent penetrant, magnetic particle, ultrasonic, radiography) with acceptance criteria and inspector qualifications as required
• CT scanning or X-ray reports for AM parts where internal features, porosity limits, or powder entrapment risk must be verified
• Indications disposition and rework/repair records when allowed

Nonconformance and corrective actions
• Any nonconformance reports (NCRs), root cause notes, and approved dispositions (use-as-is, repair, rework) if allowed by contract
• Documentation showing that final acceptance was achieved after corrective actions, with re-inspection results clearly identified

Practical tip for AM + machining builds: In hybrid manufacturing, the FAI should clearly separate requirements verified in the as-printed/near-net condition (if applicable) vs. those verified after HIP/heat treat and final CNC machining. Distortion control, stock allowance strategy, and datum establishment are frequent risk areas that buyers will scrutinize when qualifying AM-derived hardware.

Balloon drawings and characteristics

A “ballooned drawing” is the backbone of a usable FAI. Each balloon number corresponds to a specific requirement—dimension, GD&T control, note, material callout, process requirement, inspection requirement, marking, and packaging requirement if specified. The goal is to ensure nothing on the engineering definition is missed and that every requirement has objective evidence.

What should be ballooned?

1) Every measurable dimension and GD&T control. Include feature control frames, datum references, position/profile/flatness/perpendicularity, runout, and any implied requirements that your customer expects treated as characteristics. For complex 5-axis parts, capture compound datum schemes and multiple setups.

2) All drawing notes that impose acceptance criteria. Common examples: surface finish, edge break/deburr requirements, plating/coating, paint, marking, cleanliness, and torque/assembly instructions when they apply to delivered configuration.

3) Material and process notes. Alloy/temper, heat treat, HIP requirements, coating specs, and NDE requirements are “characteristics” in the sense that they must be verified and documented—often via certs and reports rather than a micrometer.

4) Key characteristics (KCs) / critical characteristics (CCs). If the customer identifies KCs/CCs, they should be flagged in the ballooning approach and may require enhanced control plans (SPC, 100% inspection, capability studies) during and after FAI.

How to define a “characteristic” in practice

High-performing aerospace suppliers create an internal characteristic list that aligns with the drawing and the manufacturing plan. A useful approach is to categorize characteristics by verification method:

• Dimensional: verified by CMM, optical scanning, gage, hand tools
• Material: verified by mill certs, chemistry/mechanical test reports, powder lot COA, witness coupons (AM), or additional testing
• Process: verified by process certs (HIP/heat treat/coating), NADCAP certs, furnace charts, or traveler sign-offs
• NDE: verified by inspection reports and indication maps
• Identification/packaging: verified by photos, marking inspection, and packaging checklists if called out

Ballooning pitfalls that create avoidable FAI churn

• Missing note ballooning. Many FAI issues occur because teams balloon only dimensions but overlook notes such as “Break all sharp edges 0.005–0.015,” “No nicks,” “Mask these surfaces,” or “Inspect to X standard.” These must be captured and closed.

• Ambiguous characteristic breakdown. A single note can contain multiple requirements (e.g., coating type, thickness, adhesion test, bake-out). Break it into multiple characteristics so each has a clear evidence artifact.

• Datum misunderstanding. If the CMM program establishes datums differently than the drawing intent, you can “pass” dimensions but still fail the customer’s review. Include a short explanation of datum simulation and fixturing that matches the part’s functional interfaces.

AM-specific characteristic control example: For PBF parts with internal channels or lattices, characteristics may include minimum wall thickness, internal passage diameter, powder removal confirmation, and internal surface condition. These are often best verified through CT scanning on the FAI lot, combined with documented powder removal steps and acceptance criteria tied to the drawing/spec.

Common causes of FAI failure

FAI “failure” can mean different things depending on the customer: dimensional nonconformance, missing objective evidence, inadequate traceability, or a mismatch between build configuration and the released engineering definition. In many cases, the part is physically acceptable but the package is not—leading to delays, rework, or a re-submission.

The most common failure modes in aerospace FAIs include:

1) Incomplete characteristic coverage. Missing balloons, missing inspection results, or unclosed notes are frequent. Buyers often reject an FAI because one requirement has no documented closure—even if all critical dimensions are correct.

2) Measurement method mismatch. Using an inspection method that cannot reliably support the tolerance (e.g., hand tools for tight position/profile requirements) invites disputes. For tight GD&T on complex surfaces, CMM or validated scanning workflows are typically expected. Where scanning is used, document alignment strategy, datum simulation, filtering, and acceptance criteria.

3) Uncontrolled or undocumented process changes. If the traveler shows a different heat treat, an alternate cutting tool path, or a changed HIP vendor versus the approved plan—and the package doesn’t clearly justify it—reviewers may treat it as a new configuration requiring re-FAI.

4) Weak material traceability. For AM, traceability gaps often occur around powder handling: mixed powder lots, unclear virgin/reused powder ratios, missing powder sieve records, or insufficient linkage between powder lot, build ID, and part serial numbers. For subtractive builds, the issue is usually missing heat/lot tie-in from raw stock to finished parts.

5) Special process evidence gaps. Missing furnace charts, incomplete NADCAP documentation (where required), or unclear certification pack traceability (which parts were in which batch/charge) can stop acceptance. HIP and heat treat charge traceability are especially important when multiple parts share a cycle.

6) AM distortion and machining allowance errors. A common hybrid manufacturing issue: the as-printed geometry distorts after stress relief/HIP, leaving insufficient stock for machining or causing datum surfaces to shift. The FAI then shows out-of-tolerance conditions on features that would otherwise be straightforward. This is preventable with robust distortion compensation, machining stock strategy, and inspection gates before expensive finishing.

7) NDE scope and acceptance criteria confusion. If the drawing calls out NDE to a specification level and the report does not clearly state the method, sensitivity, acceptance criteria, and result disposition, the FAI may be rejected. For CT, the scan resolution (voxel size) and the defect/feature thresholds must be appropriate to the requirements.

8) Documentation and configuration control errors. Wrong revision level, mismatched part marking, missing customer approvals for deviations, or outdated inspection plans are classic causes of FAI rejection—particularly in regulated programs with strict change control.

Operational takeaway: Treat FAI as an integrated deliverable. Build a checklist that combines drawing requirements, traveler route steps, and contract clauses. A technically perfect part can still fail if the compliance story is incomplete or inconsistent.

Managing revisions

Aerospace programs change—design optimization, weight reduction, supplier transitions, and lessons learned from testing frequently drive revisions. The goal is to respond to revisions without unnecessary resets, while still maintaining configuration integrity and buyer confidence.

Best practices for managing revisions in an FAI context:

1) Classify changes by impact. Create a simple internal decision tree:• No-impact changes (e.g., typo corrections with no requirement change) may require documentation updates but not re-measurement.
• Localized requirement changes (a tolerance change on one feature) usually require a partial/delta FAI on impacted characteristics plus any dependent datums or linked features.
• Process-affecting changes (material, heat treat, coating, build orientation, machine change) often require broader re-validation because they can influence multiple characteristics.

2) Preserve the baseline and show the delta. When submitting a partial FAI, clearly reference the prior approved FAI and provide a crosswalk showing which balloon numbers are being re-verified and why. Avoid forcing the reviewer to compare documents manually.

3) Tie revision control to the manufacturing plan. For hybrid AM + machining, revision control must cover:• PBF build file/version, scan strategy, orientation, supports, and parameter set
• Post-processing route (stress relief, HIP, heat treat, surface treatment)
• CNC programs, fixtures, probing routines, and datum pick-up strategy
• Inspection programs (CMM code version, scanning templates, CT scan recipe)

4) Re-validate datums when interfaces change. If a revision affects a datum feature or a functional interface, do not assume a small change is isolated. Datum shifts can cascade into positional/profile results across multiple features.

5) Control rework and repair across revisions. If a part was built to Rev A but reworked to Rev B, document the transition carefully and confirm the customer will accept that path. Many aerospace customers require the part to be manufactured fully to the current revision unless a deviation is approved.

6) Align with quality management system requirements. Under AS9100 practices, revision management is not only an engineering function—quality and manufacturing must confirm that released documents, routers, and inspection plans are updated and that obsolete versions are removed from point of use. This discipline prevents “mixed configuration” FAIs that fail review.

Buyer/supplier workflow

A clean buyer/supplier workflow is the fastest way to get through FAI with minimal rework and minimal schedule risk. The most successful programs treat FAI as a joint planning activity, not a surprise deliverable at the end.

Step 1: RFQ and contract review (set expectations early)
At RFQ, the buyer should specify: required FAI format, whether partial FAIs are acceptable for future changes, key characteristics, NDE expectations, and any program-specific requirements (e.g., ITAR handling, DFARS compliance, serialization rules). The supplier should respond with: proposed manufacturing route (including AM vs. conventional), inspection approach, planned gages/CMM/CT capability, and lead time impacts of HIP, heat treat, and external NADCAP processes.

Step 2: Supplier qualification and capability confirmation
Before cutting metal (or printing powder), confirm that the supplier’s QMS and process approvals match the program needs:
• AS9100 certification status (if required)
• Special process approvals and whether external processors are approved sources
• NDE capability and qualification (including subcontractor controls)
• ITAR controls for controlled technical data and physical hardware (segregation, access control, training, visitor controls)

Step 3: Manufacturing planning (define the “as-built” route)
Supplier creates the router/traveler with clear inspection gates. For hybrid AM builds, a practical gate structure is:
• Incoming material/powder verification and lot assignment
• Build execution records (machine ID, parameter set, build ID)
• Post-build operations (support removal, stress relief)
• HIP (or PM-HIP densification) with charge traceability and chart retention
• Rough machining to establish datums and remove distortion-sensitive stock
• Intermediate inspection (CMM or scanning) to confirm stock and datum quality
• Finish machining, surface finishing, and marking
• Final inspection + NDE + packaging

Step 4: Inspection planning (ballooning and method selection)
The supplier (or buyer, depending on contract) balloons the drawing and builds the characteristic accountability list. Define method-of-measurement for each characteristic. For complex geometries, align early on whether the customer accepts point-based CMM, scan-based surface comparison, or a combination. If CT scanning is part of acceptance, lock down resolution and reporting format up front.

Step 5: Build the first article with production-intent controls
FAI should be produced using the same controls intended for production: approved work instructions, trained operators, calibrated equipment, controlled powder handling for AM, and controlled special process sources. “Prototype shortcuts” often become the root cause of FAI delays because they create an as-built configuration that cannot be repeated or audited.

Step 6: Compile the FAI package (objective evidence + traceability)
As data is generated, compile it into a coherent pack rather than collecting it at the end. Include clear references from each balloon number to the evidence: CMM report page/feature ID, surface finish log entry, heat treat chart ID, HIP charge number, NDE report number, etc. Ensure all documents share consistent identifiers (part serial, lot, work order).

Step 7: Internal review and “FAI readiness” audit
Before submission, run a short internal audit that asks:• Are all balloons accounted for and closed?
• Do the measured results clearly meet acceptance criteria?
• Are any dispositions present, and are they customer-approved?
• Is material traceability complete from raw material/powder to finished part serial?
• Are special process records complete, legible, and traceable to the part?
• Are all revisions correct and consistent?

Step 8: Buyer review, feedback loop, and approval
Buyers should review FAIs as a technical and quality approval. If issues are found, provide structured feedback referencing characteristic numbers and required evidence. Suppliers should respond with corrected data, root cause (if needed), and a clear plan for maintaining control in production.

Step 9: Transition to production control
Once approved, lock the baseline: manufacturing plan, inspection plan, and special process sources. For key characteristics, implement ongoing controls (SPC where appropriate, periodic CMM audits, powder reuse limits for PBF, periodic CT sampling plans). FAI is the starting point for production control—not the end of quality planning.

Procurement-ready outcome: The best FAIs don’t just prove the part meets the drawing; they prove the system—people, equipment, processes, and records—can repeatedly produce compliant aerospace hardware under controlled configuration. That is what ultimately reduces risk for engineers, program managers, and sourcing teams.