A realistic answer is: it varies widely, and any single percentage without scope is usually misleading.
In aerospace manufacturing, reported cost of poor quality often lands somewhere in the low single digits of revenue or manufacturing cost for relatively mature, well-controlled programs, and can rise much higher on unstable launches, high-complexity assemblies, low-volume builds, supplier-disrupted programs, or operations with weak cost capture. If someone gives you one benchmark number as universally “normal,” treat it cautiously.
The more important point is that COPQ in aerospace is usually undercounted. Scrap and logged rework are easy to see. Harder costs are often spread across labor overruns, queue time, engineering support, MRB activity, concession handling, first article repetition, inspection burden, supplier escapes, schedule disruption, expedited freight, and excess WIP. Those costs may sit in different systems and cost centers, so the reported percentage can look artificially low.
What is realistic in practice
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Mature, repeatable production: often low single digits if the plant has disciplined cost collection and relatively stable processes.
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Programs under strain: mid single digits or higher is not unusual when rework, supplier quality issues, engineering churn, or documentation gaps are significant.
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New product introduction, qualification-heavy work, or complex assemblies: COPQ can be materially above that, especially early in ramp, because defect discovery is expensive and each correction may trigger traceability, review, and downstream schedule effects.
That does not mean one plant is necessarily “better” than another. A site that measures more honestly may report a higher COPQ than a site that only counts scrap and direct rework hours.
What drives the number
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Program maturity and rate stability
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Product complexity and critical characteristics
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Supplier quality and incoming variation
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How much rework is routable and costed versus handled informally
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How MRB, deviations, concessions, and containment costs are tracked
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Whether engineering changes are frequent and well controlled
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How integrated MES, ERP, QMS, and labor reporting actually are
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Whether the organization includes only factory-floor losses or also administrative and schedule-recovery costs
In regulated aerospace environments, traceability and change control add real overhead to every quality event. That is operationally necessary, but it also means a defect is often more expensive than the same defect would be in a less regulated sector.
Why benchmarking is hard
COPQ percentages are highly sensitive to the denominator and the inclusion rules. Some teams calculate against sales, some against value added, some against conversion cost, and some against total manufacturing cost. Some include warranty or field issues; some do not. Some include supplier recovery offsets; some report gross cost. Without a common method, comparisons across plants, business units, or suppliers are weak.
Brownfield system reality makes this worse. In many aerospace operations, scrap may be visible in ERP, nonconformance records live in QMS, rework execution sits in MES or paper travelers, supplier escapes are tracked elsewhere, and engineering support is buried in labor or overhead. Full system replacement rarely fixes this quickly in regulated, long-lifecycle environments because qualification burden, validation cost, integration complexity, and downtime risk are high. In practice, most sites improve COPQ visibility through staged integration, better event coding, and tighter evidence trails rather than a clean-slate replacement.
What to use instead of a generic benchmark
If you need a realistic target, start with your own baseline and define COPQ explicitly. Then separate at least these buckets:
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Internal scrap
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Rework and repair labor
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MRB and disposition effort
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Supplier nonconformance impact
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Containment and inspection overhead
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Expedites and schedule recovery
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Repeat first article or documentation-driven quality costs where relevant
That usually gives leadership a more useful view than asking for a single “good” percentage.
So, if the question is whether there is a standard aerospace COPQ number you should expect everywhere, the answer is no. A realistic range may run from low single digits on stable programs to materially higher on stressed or immature programs, but the reported figure is only as credible as the cost definition, data completeness, and system integration behind it.