How to Answer a CAR From an Aerospace Prime: Separating Occurrence From Escape

A CAR, or corrective action request, from an aerospace prime asks two questions: why the nonconformance occurred, and why it escaped to the prime. To answer it, contain first, tell the prime about other suspect deliveries, verify a separate cause for each question, then return corrective actions and evidence on the prime's form.

This guide is for quality teams at suppliers to aerospace and defense primes. The method is the same whatever your prime calls the document: CAR, SCAR, RCCA or 8D.

What is a CAR from a prime?

It is the prime's formal request that you find and remove the cause of a nonconformance on what you delivered. AS9100D clause 10.2 is where it comes from: as Lockheed Martin UK's supplier guidebook summarizes it, an organization has to flow corrective action requirements down to an external provider responsible for a nonconformity, and take specific action when timely and effective correction doesn't happen.

Some primes also require the 8D method by name, and AS13000 sets out those requirements for suppliers. Our guide to the 8D covers each discipline. Clause numbers here refer to AS9100D. Its planned successor, IA9100, has been targeted for around late 2026, so check which revision your certificate and contract cite.

What is the difference between occurrence and escape?

Occurrence is why the defect was created. Escape is why it got past your controls. They happen at different points in your process, usually have different owners, and almost always have different causes.

AS13000A calls the first the generation point and defines the escape point as the "earliest point in the process where the problem should have been detected." It expects you to find both.

Here is an invented example. A prime's receiving inspection finds bore position out of tolerance on 6 parts.

Occurrence: The fixture locator on a mill had worn past its replacement interval, so bores drifted. Why was it still in use? The maintenance plan tracked calendar time and this fixture's wear follows cycle count.
Escape: A CMM checks that bore, but second shift was running an old program revision that didn't measure it to the current requirement. Why? Nothing tied the program revision on the machine to the revision on the traveler.

Replacing the locator stops this defect. It does nothing about the CMM, which will pass the next bad feature too. Fixing the CMM catches the defect in-house and leaves you making scrap.

Why can't a single root cause answer both?

Because no single action closes both gaps. If you submit one cause, the reviewer's next question is the other half. The Lockheed guidebook puts the reason for non-detection inside D4 itself. If your prime's form has a single root cause box, write both inside it, labeled.

What kinds of escape are there?

Find out which kind you have, because each one needs a different fix:

A control existed and failed. The gauge was out of calibration, the program was the wrong revision, or the inspection step was skipped. Ask why that was possible.
A control existed but could not see the defect. The measurement isn't capable at that tolerance, the sampling plan missed a low-rate defect, or the feature is checked after it has been hidden.
No control existed. Nobody planned to look at this characteristic here. Practitioners call this a blind spot. Go back to your PFMEA and control plan.

Does there need to be a third, systemic cause?

Many primes expect one. AS13000's template asks what in your policies, procedures or systems let the problem both occur and escape. In the example, why does the change process release a new program revision without confirming it reached every shift? That answer is the one that protects other part numbers.

Is a CAR the same as a notification of escape?

No. A CAR comes from the prime to you. A notification of escape, or NoE, goes from you to the prime when you learn that delivered product is, or may be, nonconforming. SupplyOn's NoE manual describes it as the standard way to warn a customer quickly about product already delivered.

The deadline is in your contract, so read your flow-downs. As one example, Boeing's clause Q640 requires written notice for known or suspected nonconformance on delivered product within three business days of knowing the required details, and immediately for a possible safety-of-flight condition. It asks for:

The affected process or product numbers and names.
The condition and the engineering requirement it fails.
Quantities, shipping dates, purchase orders and destinations.
Serial numbers, date codes or lot numbers.

A CAR on one lot often uncovers other suspect lots. If it does, the notification obligation starts running on those lots while the CAR is still open.

What should you do first?

The Lockheed guidebook describes immediate containment as four moves: stop producing the problem, identify what is affected, quarantine it, and communicate, telling the customer if escapes are suspected.

Set the boundary using both causes. The occurrence tells you which lots may be bad, and the escape tells you which inspection records you can rely on. In the example, the CMM results from second shift can't clear those lots, so a passing report isn't evidence and those parts need re-inspection. Look at stock at your sub-tiers, in transit and at the prime as well as on your own floor.

Is rework a corrective action?

No. Replacing, repairing or reworking parts belongs in containment. Added inspection is containment too, until you can show otherwise. Check your contract before you disposition anything: primes often limit what a supplier may repair or accept as is without their approval.

How do you write the occurrence and escape causes?

Run two separate why-chains from two separate starting questions:

Occurrence chain: Why was the bore out of position?
Escape chain: Why did parts with out-of-position bores ship?

Stop when you reach something your organization can change, and the number of whys doesn't matter. Verify each link with a record: maintenance logs, travelers, CMM reports, program revision history. A cause with no record behind it is a theory, and the response should label it as one.

How should you handle human factors?

Treat them as causes to investigate. Clause 10.2 asks you to consider causes related to human factors where they apply, and "operator error" doesn't meet that. Ask about shift handover, ambiguous instructions, time pressure, tooling and workspace. Then write the cause about those conditions, without naming a person.

What makes a corrective action acceptable to a prime?

AS13000 expects corrective actions at both the generation and escape points, so the system detects the problem and doesn't release it again. The Lockheed guidebook adds its own tests: an action should address root and contributing causes, be workable and sustainable, carry an effectivity date, and avoid causing new nonconformances. In practice, that means a response that shows:

At least one action per cause: occurrence, escape and systemic.
An owner, a date and a first affected serial or lot for each.
A review of similar parts, machines and programs. AS9100D asks whether similar nonconformities exist or could occur.
Updates to the PFMEA, control plan, work instructions and first article records where they apply.

How do you show the fix worked?

Prove each fix separately:

Occurrence: Show the characteristic over production lots after the change, measured the same way as before, on a stable result and not one good part.
Escape: Challenge the control. Run a known-bad part through the corrected inspection and show that it fails. Show the corrected program revision in use on all shifts.

Size the window to how often the failure really appears. A short clean run proves little for an intermittent defect, as we showed in The Recurrence Problem. If the check fails, go back to D4 and find out whether the cause or the action was wrong.

What happens if the escape repeats?

Consequences grow. Expect a harder review, more evidence requests and scorecard damage, and repeat escapes can bring the prime's source inspectors onto your floor. The record also follows you into your next AS9100 audit, where an auditor can ask whether the corrective action was effective. The best protection is a response that a stranger could follow from the defect to the evidence.

How does Lattice help with prime CARs?

Lattice is AI investigation software for quality teams. It investigates each CAR from your own records, separates occurrence from escape, fills your prime's response form, and links each corrective action to the evidence that it worked. Your engineer reviews and signs. The aim is a response in days, with up to 80% of the hours back. See how it works for suppliers to aerospace and defense primes.

Sources

Lockheed Martin UK Ampthill (February 2025), Root Cause Corrective Action Problem Solving Guidebook, Issue 2. Summary of AS9100 clause 10.2, D0 to D8, containment, corrective action tests.
SAE International, AS13000A, preview, and AS13000 listing. Generation and escape points, corrective action at both.
Boeing, Clause Q640: Notification of Escapement (NoE) Process, effective 26 July 2018.
SupplyOn (May 2020), Notification of Escape (NoE), V1.8.
Benchmark Six Sigma Forum, Escape Point. Failed controls and blind spots.
Smithers (March 2026), AS9100 D Explained: What the "D" Means and What Comes Next.
Auxiliary Machines (2026), The Recurrence Problem.