What is the difference between FAI and in-process inspection?

FAI, or First Article Inspection, is a formal verification that a part or assembly produced under defined production conditions conforms to the applicable drawing, specifications, and purchase order requirements. In-process inspection is an ongoing production control activity used to check selected characteristics while work is being performed. They are related quality activities, but they serve different purposes and one does not replace the other.

FAI is a baseline verification event

In aerospace and other regulated manufacturing environments, FAI is commonly used to establish documented evidence that the manufacturing process can produce conforming product. Under AS9102-driven practices, this usually involves ballooned characteristics, measured results, material and special process evidence, and review of configuration requirements.

FAI is typically triggered by events such as a new part number, a design change, a process change, a supplier change, tooling changes, a long production lapse, or other changes defined by customer, procedure, or contract. The exact trigger rules are site-specific and customer-specific.

In-process inspection is production control

In-process inspection happens during normal manufacturing or assembly operations. It may verify dimensions, torque values, visual conditions, process parameters, documentation steps, or other control points before the work moves forward.

The goal is not to re-prove the entire product baseline every time. The goal is to detect drift, prevent downstream defects, confirm critical steps, and provide evidence that the controlled process was followed. The frequency may be 100 percent inspection, sampling, first-piece checks, operator self-verification, quality hold points, or automated data capture, depending on risk, process capability, customer requirements, and the control plan.

The practical difference

• FAI asks: Did the defined production process produce a part that fully matches the approved design and requirements?
• In-process inspection asks: Is the product still conforming at this step, and is the process staying under control?
• FAI is usually event-based: It occurs at initial production or after defined changes.
• In-process inspection is recurring: It is embedded in the routing, traveler, work instructions, or control plan.
• FAI is broad and configuration-focused: It ties product characteristics to drawings, specifications, materials, processes, and records.
• In-process inspection is selective and risk-based: It focuses on characteristics or steps that need control during execution.

They should connect, but they are often managed in different systems

In brownfield environments, FAI records may live in an AS9102 tool, supplier portal, quality system, PLM attachment, or customer-mandated platform. In-process inspection may be executed in MES, paper travelers, digital work instructions, SPC software, test systems, or inspection equipment. ERP may hold routing, purchase order, and lot context, while QMS may manage nonconformances and corrective actions.

This separation creates a common failure mode: the FAI proves one configuration, but production inspection plans, MES routings, or work instructions are not updated after engineering or process changes. That is a change control and data governance problem, not just an inspection problem.

Common failure modes

• FAI is treated as a paperwork exercise instead of a verification of the actual production process.
• In-process inspection checks are copied from old routings without reflecting current design risk or process capability.
• Characteristic numbering, ballooning, and inspection plans are not synchronized across PLM, MES, and quality systems.
• Partial or delta FAI requirements are missed after design, tooling, supplier, or process changes.
• Inspection results are captured but not traceable to lot, serial number, operation, equipment, gage, operator, or revision.

A mature system does not make FAI and in-process inspection the same thing. It connects them so that design characteristics, production controls, inspection evidence, nonconformance records, and change history remain traceable. In many regulated plants, that means integration and governance across existing MES, ERP, PLM, and QMS systems rather than a full replacement of the stack, which is often unrealistic because of validation cost, qualification burden, downtime risk, and long equipment lifecycles.