14 CFR Part 43: Maintenance, Repairs, and Return to Service

14 CFR Part 43 is the federal regulation that governs maintenance, preventive maintenance, rebuilding, and alterations on civil aircraft in the United States. It sets who may perform the work, the technical standards they must meet, the records they must keep, and the conditions for approving an aircraft to fly again after any technical work. If you own an aircraft, hold a mechanic certificate, or operate a repair station, Part 43 defines the boundaries of what you can legally do.

Which Aircraft Part 43 Applies To

Under 14 CFR 43.1, the regulation reaches three groups: aircraft holding a U.S. airworthiness certificate; foreign-registered civil aircraft used in common carriage or mail service under Part 121 or Part 135; and the airframes, engines, propellers, appliances, and component parts of any of those aircraft.¹ The second category catches people off guard. A Canadian-registered airliner flying scheduled service into the U.S. under Part 121 still has to meet Part 43 for its maintenance.

Several categories are excluded. Aircraft operating on an experimental airworthiness certificate are outside Part 43, unless the FAA previously issued a standard or other non-experimental certificate for that same aircraft. Small unmanned aircraft under Part 107 are excluded except where Part 107 itself requires compliance. Light-sport aircraft holding a special airworthiness certificate in that category are covered, but with lighter paperwork: they do not require the major repair and alteration form and do not follow the Appendix A and Appendix B classification lists for products not produced under an FAA approval.¹

One narrow geographic provision is worth flagging. Under 14 CFR 43.17, maintenance and alterations on U.S.-registered aircraft physically located in Canada can be performed by a Canadian-licensed maintenance engineer or a Transport Canada Approved Maintenance Organization, who may also approve the return to service. The work must still comply with Part 43, and the provision does not extend to annual inspections.²

Who Is Authorized to Perform Maintenance

Part 43 is strict about who gets to pick up a wrench. Under 14 CFR 43.3, no one may maintain, rebuild, alter, or perform preventive maintenance on a covered aircraft or component without specific authorization.³ The authorized persons fall into a handful of categories:

Certificated mechanics holding airframe or powerplant ratings, working within the scope of those ratings.
Repair stations certificated under Part 145, working within their approved ratings.
Manufacturers, on products they produced.
Pilot-owners under Part 61, limited to preventive maintenance on aircraft they own or operate (with further limits described below).

Someone without a mechanic or repairman certificate can still do hands-on maintenance work, but only under the direct supervision of a certificate holder. The supervisor has to personally observe the work to the extent needed to confirm it is being done correctly and must be readily available in person for consultation.³ Supervised workers cannot perform any inspection required by Part 91 or Part 125, and they cannot perform the inspection that follows a major repair or major alteration. Those require the certificate holder’s own hands and eyes.

Approving certain higher-consequence work takes more than a standard mechanic certificate. A mechanic who wants to sign off aircraft for return to service after major repairs, major alterations, or annual inspections needs an Inspection Authorization, which is the top individual maintenance authority the FAA issues.⁴

The Performance Standard for the Work

Section 43.13 sets the floor for how the work must be done. Anyone performing maintenance, alterations, or preventive maintenance must use the tools, equipment, and test apparatus needed to complete the job according to accepted industry practices. When the manufacturer recommends specific equipment, the person doing the work must use that equipment or an equivalent the FAA accepts.⁵

The technical data you follow is dictated by the same section. The default source is the current manufacturer’s maintenance manual or Instructions for Continued Airworthiness. When those are not available, other methods acceptable to the FAA may be used. Advisory Circular 43.13-1B is a common example, covering inspection and repair techniques for nonpressurized aircraft structures, and it can even serve as approved data for major repairs when the techniques are appropriate to the product, directly applicable to the repair, and not contrary to manufacturer data.⁶

The end result required by §43.13 is that after any maintenance or alteration, the aircraft or component must be in a condition at least equal to its original or properly altered state, in terms of structural strength, aerodynamic function, resistance to vibration and deterioration, and other qualities affecting airworthiness.⁵ Work that cuts corners on methods or data fails this standard even if the aircraft flies fine afterward.

Major vs. Minor Repairs and Alterations

Part 43 draws a hard line between major and minor work, and the distinction drives who can approve the return to service and what paperwork is required. Appendix A lays out what counts as major.

Major airframe alterations include changes to wings, tail surfaces, fuselage, engine mounts, control systems, landing gear, or hull and floats. Also major: changes to empty weight or balance that push past the aircraft’s certificated limits, changes to fuel or electrical system designs, and modifications to control surfaces that affect flutter characteristics.⁷ On the powerplant side, major alterations include converting an engine from one approved model to another, replacing structural engine parts with non-OEM parts not specifically approved by the FAA, and converting an engine to a different fuel grade than its specifications call for.

Anything not listed in Appendix A is minor. The practical consequence: minor work can be approved for return to service by any appropriately rated mechanic, while major repairs and major alterations require a certificated repair station, the manufacturer, or a mechanic holding an Inspection Authorization.⁸ Major work also triggers FAA Form 337.

Preventive Maintenance a Pilot-Owner Can Perform

You do not need a mechanic certificate for everything. Under 14 CFR 43.3(g), any pilot certificate holder under Part 61 (other than sport pilots) may perform preventive maintenance on an aircraft they own or operate, as long as it is not being used under Part 121, 129, or 135. Sport pilots have a narrower allowance: preventive maintenance only on an aircraft they own or operate that holds a special airworthiness certificate in the light-sport category.⁹

Appendix A, paragraph (c) lists the specific tasks that qualify. The full list runs to 32 categories, all limited to work that does not involve complex assembly operations.⁷ Common examples include:

Adding engine oil and removing and replacing oil filters.
Removing and replacing tires, servicing wheel bearings, and checking tire pressure.
Replacing or cleaning spark plugs and setting gap clearance.
Replacing defective safety wiring or cotter pins.
Replacing side windows (where it does not interfere with structure or operating systems) and replacing seats with approved parts, without disassembling primary structure.
Replacing and servicing batteries.
Replacing bulbs, reflectors, and lenses of position and landing lights, and troubleshooting broken landing light wiring circuits.
Replacing non-hydraulic hose connections and prefabricated fuel lines.

If you do this work yourself, you still have to make a maintenance record entry, and you are responsible for approving the aircraft for return to service. Skip the logbook entry and the aircraft is technically unairworthy, even if the work itself was perfect.

Maintenance Records and Form 337

Part 43 treats recordkeeping almost as seriously as the physical work. Sloppy paperwork can ground an aircraft just as effectively as a cracked spar.

Routine Maintenance Entries

Under 14 CFR 43.9, every person who performs maintenance, preventive maintenance, rebuilding, or alteration must make an entry containing a description of the work performed (or a reference to FAA-acceptable data), the date the work was completed, and the name of the person who did the work if different from the person approving it. The person approving the work adds their signature, certificate number, and the kind of certificate they hold. That signature is the approval for return to service, but only for the work actually performed.¹⁰

Inspection Entries

Section 43.11 governs a different situation: inspections conducted under Part 91, Part 125, or certain Part 135 provisions. The entry must record the type and extent of the inspection, the date and total aircraft time in service, and the signature and certificate information of the person approving or disapproving. A passing aircraft gets a statement certifying it was inspected and found airworthy. A failing aircraft gets a statement that a list of discrepancies has been provided to the owner.¹¹

FAA Form 337

Major repairs and major alterations require an additional layer of documentation on FAA Form 337. The person who performs or supervises the work prepares the form, which creates a permanent record of changes that could affect weight, balance, structural strength, or flight characteristics.¹² The form certifies that the work was done in accordance with Part 43.¹³ One copy stays with the aircraft records and another goes to the FAA. Missing or incomplete 337s are among the most common problems found during pre-purchase inspections and can hit resale value hard.

Retention

Owners and operators have retention obligations under 14 CFR 91.417. Routine maintenance and inspection records must be kept until the work is repeated or superseded. Records showing total time in service, current status of life-limited parts, time since last overhaul, and current inspection status must be kept and transferred with the aircraft when it changes hands. Records of major alterations and major repairs must be retained indefinitely, traveling with the aircraft for its entire service life.

Approving the Aircraft for Return to Service

Finishing the physical work is not the same as making the aircraft legal to fly. Under 14 CFR 43.5, no one may approve an aircraft for return to service after maintenance, rebuilding, or alteration unless the required maintenance record entry under §43.9 or §43.11 has been made, any required repair or alteration form has been properly completed, and any operating limitations or flight manual data affected by the work has been updated.¹⁴

Section 43.7 specifies who can sign that approval. For routine maintenance and minor repairs, a mechanic with appropriate ratings, a repairman, or a repair station can do it. For major repairs and major alterations, the signer must be a repair station, a manufacturer, or a mechanic with an Inspection Authorization, and the IA holder must verify the work was done in accordance with FAA-approved technical data.⁸ The signature carries legal weight. If the FAA later finds the work deficient, that signature points directly back to whoever approved it.

Post-Maintenance Test Flights

Some work goes beyond a parts swap and could change how the aircraft handles. Under 14 CFR 91.407, when maintenance, rebuilding, or alteration may have appreciably changed the aircraft’s flight characteristics or substantially affected its operation in flight, someone must fly an operational check before any passengers (other than required crew) are carried. The pilot performing the check must hold at least a private pilot certificate with appropriate ratings and must log the flight in the aircraft records.¹⁵

The check can be skipped when ground tests and inspection conclusively demonstrate that the work did not appreciably change flight characteristics or substantially affect flight operations.¹⁵ Replacing a landing light bulb does not require a test flight. Rebuilding a flight control surface almost certainly does. The middle ground is where judgment matters.

Penalties for Violations

The FAA has real enforcement tools when Part 43 is violated. Certificate action is the immediate threat to mechanics and repair stations. The agency can suspend or revoke a mechanic certificate, repair station certificate, or Inspection Authorization for substandard work, falsified records, or work performed beyond the scope of the authorization.

Civil penalties are the financial side. Under the FAA Reauthorization Act of 2024, which amended 49 U.S.C. 46301, the maximum civil penalty for an individual is $100,000 per violation and $1,200,000 per violation for an organization.¹⁶ Each day a violation continues counts as a separate violation, so the numbers compound quickly. Most individual enforcement cases settle well below the statutory maximum, though certificate suspension or revocation often hurts more than a fine because it takes the mechanic’s livelihood with it.

Falsifying maintenance records has its own prohibition under 14 CFR 43.12. Intentionally making a fraudulent or false entry in any maintenance record is one of the more serious maintenance violations the FAA pursues. Correcting a logbook error you discover is straightforward. Altering records to cover up deficient work ends careers.

1
eCFR. 14 CFR 43.1 – Applicability
2
eCFR. 14 CFR 43.17 – Maintenance, Preventive Maintenance, and Alterations Performed on U.S. Aeronautical Products by Certain Canadian Persons
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eCFR. 14 CFR 43.3 – Persons Authorized to Perform Maintenance, Preventive Maintenance, Rebuilding, and Alterations
4
eCFR. 14 CFR 65.91 – Inspection Authorization
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eCFR. 14 CFR 43.13 – Performance Rules (General)
6
Federal Aviation Administration. Advisory Circular 43.13-1B – Acceptable Methods, Techniques, and Practices – Aircraft Inspection and Repair
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eCFR. 14 CFR Part 43 – Appendix A, Major Alterations, Major Repairs, and Preventive Maintenance
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eCFR. 14 CFR 43.7 – Persons Authorized to Approve Aircraft for Return to Service
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eCFR. 14 CFR 43.3 – Persons Authorized to Perform Maintenance, Preventive Maintenance, Rebuilding, and Alterations
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Federal Aviation Administration, DOT. 14 CFR 43.9 – Content, Form, and Disposition of Maintenance Records
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eCFR. 14 CFR 43.11 – Content, Form, and Disposition of Records for Inspections
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Federal Aviation Administration. Advisory Circular 43.9-1G – Instructions for Completion of FAA Form 337
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Federal Aviation Administration. FAA Form 337 – Major Repair and Alteration
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eCFR. 14 CFR 43.5 – Approval for Return to Service
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eCFR. 14 CFR 91.407 – Operation After Maintenance, Preventive Maintenance, Rebuilding, or Alteration
16
Office of the Law Revision Counsel. 49 U.S. Code 46301 – Civil Penalties