01Why records are the asset
Two aircraft of the same type, same age and same physical condition can differ in value by a sum large enough to reshape a transaction, purely on the state of their paperwork. This is not a quirk of the market. It follows from a simple fact: at an audit, a sale, a financing or a lease return, nobody inspects the aircraft first — they inspect the records. The physical asset is only worth what can be demonstrated about it.
The consequences are measurable and public. In general aviation, missing logbooks are commonly assessed at around 20% of an aircraft’s retail resale value. One Fortune 100 operator paid over $500,000 to replace missing 8130-3 tags. In commercial leasing, records deficiencies are the dominant cause of redelivery overspend, and incomplete back-to-birth traceability on five life-limited parts produced a $135,000 price reduction on a single engine, alongside likely rejection at redelivery.
The asymmetry that makes this worth engineering around: a records gap costs a fraction of a percent to prevent and a substantial percentage of asset value to discover late.
Most organisations treat records as documentation about the aircraft. The more useful framing is that records are the only available evidence of state — is it airworthy, what is outstanding, what has been done, what is missing. A pile of scanned PDFs satisfies the first framing and fails the second entirely, which is why digitisation alone rarely solves the problem anyone actually has.
02What the record system must contain
Both systems specify content. They organise it differently, and the difference matters when you are reconciling a mixed fleet.
EASA — M.A.305
M.A.305 requires an aircraft continuing airworthiness record system, structured around: the certificate of release to service on completion of maintenance; the content of the record system itself — aircraft, engine and propeller logbooks, life-limited component records, the technical log; aircraft identification and time-in-service entries; and the current status items:
- Airworthiness directives and measures mandated by the competent authority in immediate reaction to a safety problem.
- Modifications and repairs.
- Compliance with the aircraft maintenance programme.
- Life-limited components.
- Mass and balance.
- The deferred maintenance list.
Separately, M.A.306 requires an operator’s technical log system for commercial air transport, commercial specialised operations and commercial ATO or DTO operations — carrying information about each flight necessary for continued flight safety, the current CRS, the current maintenance statement showing what scheduled and out-of-phase maintenance is next due, and all outstanding deferred defect rectifications. The initial issue of the technical log system must be approved by the competent authority, as must each subsequent amendment.
FAA — 14 CFR 91.417
The FAA splits records into two sets, and the split is the whole point of the rule.
| Set | Reference | Content |
|---|---|---|
| Work records | 91.417(a)(1) | Records of maintenance, preventive maintenance and alteration, and of the 100-hour, annual, progressive and other required inspections — containing a description of the work performed (or reference to acceptable data), the date of completion, and the signature and certificate number of the person approving return to service. |
| Status records | 91.417(a)(2) | Total time in service of airframe, each engine, propeller and rotor; current status of life-limited parts; time since last overhaul of items overhauled on a time basis; current inspection status including time since the last required inspection; current status of applicable ADs and safety directives, including method of compliance, AD number and revision date, and for recurring items the time and date the next action is required; and copies of FAA Form 337 for each major alteration. |
The content of individual entries is set by 14 CFR 43.9 for maintenance, and 14 CFR 43.11 for inspections — the latter requiring the type and extent of the inspection, the date and aircraft total time in service, the signature and certificate number, and the prescribed airworthy or not-airworthy certification statement. Where an aircraft is found unairworthy, 43.11(b) requires the person to give the owner or lessee a signed and dated list of discrepancies.
Read 91.417(a)(2)(v) carefully. It requires, for each applicable AD: the method of compliance, the AD number and revision date, and for recurring directives the time and date when the next action is required. A spreadsheet listing AD numbers and a tick does not meet this. In particular, recording the revision date is what allows anyone later to determine whether the determination was made against the AD text that is currently in force — and that is exactly the question a superseded or revised AD raises.
03Retention: how EASA and the FAA cut it differently
This is the single most misquoted area in technical records, usually reduced to “12 months versus 36 months”. That comparison is wrong because the two regimes divide records along different lines.
The EASA detail worth knowing
M.A.305(e) requires the owner or operator to establish a system to keep specified documents and data in a form acceptable to the competent authority. The recurring formula for detailed maintenance records is not a flat period but a condition: records are kept “until such time as the information contained therein is superseded by new information equivalent in scope and detail but covering a period not shorter than 36 months”. That applies to records demonstrating AD compliance, and to records of scheduled maintenance and other maintenance required for continuing airworthiness.
The life-limited part in-service history record — on which the current status of compliance with airworthiness limitations is determined — carries no stated period. In practice it runs for the life of the part, which is the regulatory foothold underneath what the market calls back-to-birth.
Do not cite “M.A.305(h)” for retention. Older Part-M, before Regulation (EU) 2019/1383, put retention in M.A.305(h) with a six-item list. Many secondary sources and derivative national rulebooks still reflect that structure. The current point is M.A.305(e).
Do not rely on UK-retained renderings for EU-current text. UK-retained law is frozen at 31 December 2020, substitutes national terminology for “competent authority” and “EASA Form 1”, and omits post-2020 additions. Verify against the EASA Easy Access Rules for Continuing Airworthiness before quoting verbatim.
04Transfer on sale — and the clock that does not reset
M.A.307 governs transfer, and one of its three paragraphs deserves particular attention.
- (a) On permanent transfer from one owner or operator to another, the transferring party must ensure the
M.A.305continuing airworthiness records and, if applicable, theM.A.306technical log system are also transferred. - (b) Where the owner contracts continuing airworthiness management to a CAMO or CAO, the owner must ensure the records are transferred to that organisation.
- (c) The retention periods set out in
M.A.305(e)continue to apply to the new owner, operator, CAMO or CAO.
Paragraph (c) is the one that catches people. Transfer does not reset the clock. A buyer acquiring an aircraft acquires the outstanding retention obligations along with it, measured from the original events — not from the date of purchase.
The FAA equivalent is a separate section, 14 CFR 91.419, commonly conflated with 91.417. It requires the seller of a US-registered aircraft to transfer to the purchaser at the time of sale the 91.417(a)(2) status records, and those 91.417(a)(1) work records not already covered — though the purchaser may permit the seller to keep physical custody of the work records. Custody by the seller does not relieve the purchaser of the obligation to make records available for inspection.
05Back-to-birth traceability
Back-to-birth traceability means documentation showing the provenance of the accumulated cycles or time on a part since its first operation — every owner and every installation, all the way back to manufacture.
It matters most for engine life-limited parts, whose commercial value is a direct function of remaining life. That value has created a specialised trading market, and back-to-birth documentation has a significant impact on the asset value and marketability of the aircraft. For lessors specifically, the two drivers are remarketability — the ability to transition an aircraft between regulatory jurisdictions without friction — and residual value impairment.
Back-to-birth traceability is not a regulatory requirement. Many regulatory authorities have no general back-to-birth requirement, and air carriers are free to establish alternative systems for establishing and tracking the time on parts. It is standard industry practice, imposed contractually by lessors, financiers and buyers because of its effect on value — not an airworthiness obligation of the FAA, EASA or ICAO.
This distinction has a practical consequence. An operator who has satisfied its regulator entirely may still be holding an asset that a lessor will not accept, because the two are measuring different things. If you are buying, leasing or financing, the requirement has to be written into the contract — it will not arrive by regulation.
What the evidence has to consist of
Industry guidance organises the required documentation into three categories:
The consequence of a break in the chain is severe and non-negotiable: if an aircraft is missing satisfactory evidence of current used life status, the affected parts must be replaced. A part with substantial physical life remaining, entirely serviceable, must be scrapped because its paper trail cannot be closed. That is the mechanism behind the $135,000 valuation haircut cited earlier, and behind the $500,000 spent replacing missing release tags.
06Release documents
FAA Form 8130-3, the Authorized Release Certificate / Airworthiness Approval Tag, and its European counterpart the EASA Form 1, are the documents that travel with a part. The 8130-3 serves three distinct functions, and conflating them is the most common error in this area:
- Airworthiness approval of new production — certifying that a newly produced article conforms to approved design and is in a condition for safe operation, issued while the article is within a Production Approval Holder’s quality system.
- Return to service after maintenance — issued by FAA-certificated organisations. Note that for domestic US purposes this use is optional: the regulatory return to service is the
14 CFR 43.9record entry, and the tag is supplementary. - Export — supporting export airworthiness approval and acceptance under bilateral agreements.
Dual release refers to a release certificate endorsed under both the FAA and EASA systems, allowing the part to be accepted in either jurisdiction without further documentation. For operators and lessors working across both registers, whether a part carries dual release determines whether it can move with the aircraft — and it is far cheaper to require dual release at the point of purchase than to obtain it retrospectively.
On the airframe side, 14 CFR 43.9(d) requires major repairs and major alterations to be recorded on FAA Form 337 and disposed of per Appendix B to Part 43 — and copies of the 337s for major alterations form part of the permanent 91.417(a)(2) status records that travel with the aircraft.
07Electronic records
The legal question is settled. The regulations specify the required content of a record, not its medium.
AC 120-78B, “Electronic Signatures, Electronic Recordkeeping, and Electronic Manuals”, dated 11 December 2024, is the current FAA guidance, cancelling AC 120-78A. It applies across 14 CFR parts 5, 43, 61, 63, 65, 91, 121, 125, 133, 135, 137, 141, 142, 145 and 147 — reaching both the maintenance side and the operator side. It is guidance: it describes an acceptable means, not the only means, and does not create an approval requirement.
An electronic signature must satisfy eight criteria:
| Criterion | What it means in practice |
|---|---|
| Uniqueness | The signature is unique to the signer — no shared accounts |
| Authentication | Means exist to identify and authenticate a particular person |
| Sole control | The signature is under the sole control of the signer |
| Intent to sign | Executed or adopted by a person with the intent to sign |
| Deliberate action | The result of a deliberate action, not a side effect of another operation |
| Non-repudiation | The signer cannot later deny having affixed it |
| Permanence | The signature is permanent and the information attached is unalterable |
| Document integrity | Once signed, the document cannot be edited |
Beyond signatures, an electronic recordkeeping system is expected to provide controlled access, record preservation, protection of confidential information, prevention of data corruption, IT support, software revision control and backup.
AC 43-9C is superseded. The canonical maintenance-records advisory circular for 27 years was replaced by AC 43-9D, “Maintenance Records and FAA Form 8130-3 Return to Service”, dated 22 September 2025. If your procedures manual, CAME or records policy cites AC 43-9C, it is out of date — and this is exactly the kind of stale reference an auditor notices immediately.
08What a defensible record actually looks like
Compliance that cannot be demonstrated is, for every practical purpose, non-compliance. A defensible record answers six questions without the reader having to reconstruct anything.
91.417(a)(2)(v) requires the AD revision date explicitly.91.417(a)(2)(v).Two further requirements come from the leasing world rather than the regulator, and they routinely block acceptance at redelivery. Records must be in the English language, and clear and legible, with corrections showing the corrected original entry — overwriting or obliterating an original entry destroys its evidential value, whatever the intention.
09Where value is destroyed
| Failure | How it happens | Control |
|---|---|---|
| Unevidenced N/A | A directive or task assessed as not applicable, closed with no recorded reasoning | Apply the same evidence standard to negative determinations as to positive ones |
| Broken LLP chain | A shop visit, transfer or storage period with no release certificate or status record | Treat every part movement as a documented event; refuse parts without the tag at the point of receipt, not later |
| Missing revision dates | AD status recorded by number only | Record the revision date on every entry — it is a regulatory requirement under 91.417(a)(2)(v) |
| Retention clock reset at sale | Buyer assumes obligations start at purchase | M.A.307(c) says otherwise. Audit inherited retention obligations during due diligence, not after |
| Records held only by the MRO | Work packs never returned, or returned incomplete | Make records return a contractual milestone and a payment condition |
| Obliterated corrections | Entries overwritten or tippexed rather than struck through | Corrections must show the corrected original entry |
| Stale AC references | Procedures citing AC 43-9C or AC 120-78A | Review external references annually; AC 43-9D and AC 120-78B are current |
| Non-English records | Local-language work packs on an aircraft destined for a cross-border lease | Establish the language requirement before the work, not at redelivery |
10Key terms
- BTB
- Back-to-birth — documentation of a part’s provenance since first operation. Contractual, not regulatory.
- LLP
- Life-Limited Part — a part with a mandatory life limit, discarded rather than restored.
- CRS
- Certificate of Release to Service — the release of maintenance in the EASA system.
- EASA Form 1
- Authorised release certificate for a part in the European system.
- FAA Form 8130-3
- Authorized Release Certificate / Airworthiness Approval Tag. Three functions: new production, return to service, export.
- Dual release
- A release certificate endorsed under both FAA and EASA systems, accepted in either jurisdiction.
- FAA Form 337
- Major Repair and Alteration record, required by 14 CFR 43.9(d); copies form part of the permanent status records.
- TSN / CSN
- Time Since New / Cycles Since New — the fundamental life measures for a part.
- TSO / CSO
- Time Since Overhaul / Cycles Since Overhaul.
- Dirty fingerprint
- Informal term for the physical evidence trail — the original signed records showing work actually happened.
- Technical log
- The operator’s per-flight record system required by M.A.306, carrying the current CRS, maintenance statement and deferred defects.
- AC 120-78B
- Current FAA guidance on electronic signatures, recordkeeping and manuals, dated 11 December 2024.
11Frequently asked questions
Can records be kept only in electronic form?
Yes, where the system meets the applicable criteria. The rules specify record content rather than medium, and AC 120-78B sets out an acceptable means of compliance for electronic signatures and recordkeeping. Under EASA, M.A.305(e) requires records to be kept “in a form acceptable to the competent authority” — which is the hook to discuss the specific system with your authority rather than assume acceptance.
What happens if logbooks are lost or destroyed?
The total time in service has to be reconstructed by other means — reference to other records reflecting time in service, research of records held by repair facilities, and reference to records maintained by individual mechanics. Reconstruction is possible but expensive and never fully restores value: in general aviation the loss is commonly assessed at around 20% of retail resale value. Where LLP used-life status cannot be evidenced satisfactorily, the affected parts must be replaced regardless of their physical condition.
Do I have to keep records forever?
Some of them, effectively yes. Under the FAA rule the 91.417(a)(2) status records — total time in service, LLP status, inspection status, AD status and Form 337s — have no expiry and are retained and transferred with the aircraft on sale. Under EASA, the LLP in-service history record carries no stated period and runs for the life of the part. The records with defined periods are the transactional ones: the technical log and the detailed maintenance records.
Who owns the records — the operator, the owner, or the MRO?
Regulatory responsibility for the record system sits with the owner or operator under M.A.305. The MRO holds work packs during and after the work but has no ownership claim beyond its own retention obligations. In practice the problem is not ownership but possession: work packs that never come back, or come back incomplete, are a routine cause of gaps. Make records return a contractual milestone tied to payment.
Is a scanned copy acceptable?
Generally yes, subject to the same integrity, access and retention expectations as any electronic record. The more important question is usually not whether the scan is acceptable but whether it is sufficient: a searchable pile of images tells you what documents exist, not whether the aircraft is airworthy, what is outstanding, or what is missing. Those are questions about computed state, and no scanning process answers them.
What language must records be in?
There is no universal regulatory answer, but the commercial answer for any aircraft that may be leased or sold internationally is English. Lease agreements routinely require records to be in the English language, clear and legible, with corrections showing the corrected original entry, and in a format complying with generally accepted international commercial airline practice. Discovering a language requirement at redelivery is expensive; establishing it before the work is free.