FAA Form 337 Example: Signatures, Distribution, and Rejections

A completed FAA Form 337 example has three things right: the aircraft identification blocks match the registration certificate exactly, Item 8 describes the work and cites the approved data that authorized it, and the two signature blocks are signed by people with the correct authority. Get those right and the form clears validation at the FAA Aircraft Registration Branch. Miss any of them and the form comes back for correction, which delays the aircraft’s return to service.

The form is used to record a major repair or major alteration on a U.S.-registered aircraft, engine, propeller, or appliance. Below is a walk through each block in the order you’ll fill it in, with the traps that most often send forms back.

Items 1 Through 4: Aircraft Identification

The top of the form ties the document to a specific aircraft. The FAA registry cross-checks the N-number against the serial number automatically, so a single transposed digit here triggers a rejection.

Item 1 asks for the aircraft’s nationality and registration mark (the N-number), make, model, and serial number. Every field must match what appears on your Certificate of Aircraft Registration, FAA Form 8050-3.¹ The make, model, and serial number also appear on the manufacturer’s data plate. If you’ve recently changed your N-number and haven’t received the new registration certificate yet, use the old N-number on the form.

Item 2 is the aircraft owner’s full name and address, again matching the registration certificate exactly. Item 3 identifies the unit involved: airframe, powerplant, propeller, or appliance. Item 4 has the check boxes for whether the work is a major repair or a major alteration.

Item 8: Describing the Work

This is where most of the substance lives, and where most mistakes happen. Item 8 asks for a description of the work accomplished. Someone reading it years from now should be able to tell exactly what was done, where on the aircraft it was done, and what data authorized it.

What Item 8 Should Cover

A solid Item 8 entry covers three things:

The location of the work on the aircraft.
The materials and parts used, with part numbers.
A reference to the approved data that authorized the repair or alteration.

Approved data can take several forms: a Supplemental Type Certificate (STC), the aircraft manufacturer’s structural repair manual, an FAA-approved engineering order, or data approved through a Designated Engineering Representative (DER). For alterations, a field approval by the local Flight Standards District Office is another pathway. Block 3 on the form asks you to identify which type of approved data you used. Vague references such as “per manufacturer’s instructions” without naming the actual document are one of the top reasons forms come back.

If the work changes the aircraft’s operating limitations, note those changes. If weight and balance are affected, enter the changes in the aircraft’s weight and balance records with the date, a signature, and a reference back to the Form 337. Putting the full weight and balance computation in Item 8 is optional, not required.¹

Handling Attachments

If you need more space than the form provides, attach additional sheets. Each attachment must show the aircraft’s N-number and the date the work was completed. Keep attachments to standard 8½-by-11-inch pages. Oversized submissions get returned for reformatting.

One practical point on sequencing: if the repair involves an area that will later be covered by a skin, fairing, or other structure, have an authorized person inspect and document the work before it gets concealed. Skipping this can mean pulling panels off later to satisfy an inspector.

Items 6 and 7: The Two Signatures

The form requires two separate signatures that do different jobs. Confusing them is a common error, and both signature blocks need the signer’s certificate number and certificate type along with the signature itself.

Item 6: Conformity Statement

Item 6 is signed by the person who performed or directly supervised the work. This is typically a certificated mechanic holding Airframe and Powerplant (A&P) ratings, though the work can also be performed by a repair station or by a person working under the direct supervision of a certificated mechanic.² The Item 6 signature certifies that the work was completed as described and in accordance with the approved data referenced in Item 8.

Item 7: Approval for Return to Service

Item 7 is the higher-level signature, and a standard A&P mechanic cannot sign it for major work. Approval for return to service after a major repair or major alteration must come from someone with additional authority: a mechanic holding an Inspection Authorization (IA), a representative of a certificated repair station, an FAA Flight Standards inspector, or an FAA designee.³ The person signing Item 7 is certifying that they inspected the completed work and found it airworthy. Before signing, they must verify that everything described in Item 8 matches the approved data and that the form is complete.¹

Distribution and the 48-Hour Deadline

Once the work is done and both signatures are in place, the copies go out:

One signed copy to the aircraft owner for the aircraft’s permanent maintenance records.
A second copy to the FAA Aircraft Registration Branch in Oklahoma City, Oklahoma, within 48 hours after the aircraft is approved for return to service.

Both requirements come from 14 CFR Part 43, Appendix B.⁴ One special case adds a third copy. If the work involves extended-range fuel tanks installed inside a passenger or baggage compartment, the form must be executed in at least triplicate, with the additional copy kept on board the aircraft.⁵

The FAA also accepts electronic submission through an eForms system called E-337. Access requires coordination with your local Flight Standards District Office or International Field Office. Paper or electronic, the 48-hour clock still applies.

A separate logbook entry under 14 CFR 43.9 is still required. The Form 337 filing obligation sits on top of the standard maintenance record entry, not in place of it.⁶

Why Forms Get Rejected

Rejected forms go back to the person named in Item 6 for correction.¹ The recurring problems are:

N-number and serial number mismatch. The registry cross-checks these automatically; one wrong character sends the form back.
Missing or incomplete approved data reference in Item 8. Cite the specific STC number, manual section, or engineering order.
Oversized attachments. Anything larger than 8½ by 11 inches gets returned.
Incomplete signature blocks. Both Item 6 and Item 7 need the signer’s certificate number and certificate type in addition to the signature.

To correct a Form 337 after initial submission, file an amended form and include a statement in Item 8 identifying what was corrected, referencing the original submission date and N-number. Attach a copy of the original form for the FAA’s reference. If a Form 337 is lost, the Aircraft Registration Branch in Oklahoma City keeps copies and can supply duplicates, and can also confirm whether a specific form was received and filed.

When Form 337 Isn’t the Right Document

Two situations look like Form 337 territory but aren’t. Certificated repair stations performing major repairs under a manual or specifications acceptable to the FAA may substitute the customer’s work order for the form; the station gives you a signed work order plus a maintenance release and keeps a duplicate for at least two years.⁵ That substitution covers major repairs only. A major alteration by a repair station still requires a Form 337.

Air carriers and operators under Parts 121 and 135 use their own continuous airworthiness recording systems and generally do not use Form 337 for routine major work. If you operate under Part 91 with a standard airworthiness certificate, the Form 337 process described above is the one that applies to you.