Acquisition diligence
Closing logbook gaps found during aircraft due diligence
A logbook gap surfaced in diligence is a stretch of the aircraft's life, months or years, that the airframe, engine, or APU logbooks do not cover. This remediation bounds the gap precisely, establishes what was happening to the aircraft during it, and rebuilds the period from secondary evidence: utilization reports, maintenance invoices, flight logs, insurance and storage records, and the files of whoever operated it at the time. Acquisition and technical diligence teams use it to convert an alarming unknown into a priced, documented exposure before the deal terms are fixed. Deliverables are a gap dossier, a reconstructed utilization account, and a residual-risk statement the investment team can act on.
When this review is needed
- Diligence found a period where logbook entries simply stop, spanning an operator change or repossession.
- A records-system migration left years of history in an export nobody can open, with paper already destroyed.
- The seller claims a storage period explains the silence, and the claim needs evidence before it enters the price.
- Total-time figures at the gap's two ends do not reconcile, hinting at unrecorded operation.
The problem
The gap sits in the middle of a live deal with a signed letter of intent and an exclusivity clock running. Sellers offer explanations without documents, brokers minimize, and the diligence team knows only that between two dates the aircraft's history goes dark. Whether those months hold a quiet storage program or an unrecorded lease in a harsh operating environment changes the asset's value, and nobody currently at the table was there.
What gets reviewed
- Precise bounding of the gap: last reliable entry before, first reliable entry after, for each logbook affected
- Reconciliation of times and cycles across the gap boundaries to test for unrecorded operation
- Identification of every party with custody of the aircraft during the silent period
- Collection of secondary evidence: utilization reports, invoices, flight-tracking data, storage and insurance records
- Cross-checks of maintenance events inside the gap against MRO archives and component certificates dated within it
- A documented account of the period at the confidence level the evidence supports
Scope this review
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What gets validated
- Total time and cycles entering the gap plus reconstructed utilization equal the totals exiting it
- Claimed storage is corroborated by preservation task records, storage invoices, or insurance status changes
- Component certificates dated during the gap are consistent with the reconstructed location and operation
- Secondary sources are independent of one another rather than copies of a single unverified claim
- Regulatory filings from the period, such as registration and airworthiness events, align with the reconstruction
Evidence normally required
- The logbooks as they exist, establishing the gap's edges
- The seller's explanation of the period and any documents offered in support
- Chain-of-custody information: registrations, operators, lessees, and repossession events
- Component and engine records that may carry dates from inside the gap
- Access for outreach to prior operators, MROs, and storage facilities
Common discrepancies
- A genuine storage period, fully corroborated, that shrinks a frightening gap into a documented non-event
- Utilization during the silent months recoverable from a prior operator's dispatch or billing records
- A records-system migration where the missing entries survive in a legacy export the seller never opened
- Hour-cycle arithmetic at the boundaries that does not balance, converting a paperwork gap into a valuation issue
What is at stake
Deals absorb logbook gaps in one of three ways: a price reduction sized to the worst case, a holdback that ties up capital and goodwill, or a walk-away. All three get more expensive than a reconstruction that narrows the unknown, and a buyer who closes with the gap undocumented inherits it permanently, since the next sale will rediscover it with fewer surviving sources.
Move from findings to resolution
Sequence the fixes and the documentation that closes each finding.
How the work runs
Define the edges
Fix the last good entry and the first good entry for every affected logbook, with times and cycles at each.
Establish custody
Determine who had the aircraft during the silence and what they were doing with it.
Rebuild from independent sources
Gather utilization, maintenance, storage, and registry evidence and test it for internal consistency.
Price the residual
State what the evidence proves, what stays unknown, and what the unknown plausibly costs the deal.
What the buyer receives
- A gap dossier defining the silent period and cataloging every source consulted
- A reconstructed utilization and custody account with each element traced to independent evidence
- A residual-risk statement sized for deal negotiation: what remains unknown and what it plausibly costs
Who uses the output
- Investment committees deciding between price adjustment, holdback, and withdrawal
- Technical diligence leads folding the reconstruction into the final report
- The buyer's future records team, which inherits the dossier as the permanent account of the period
How the work fits into the transaction or program
Gap remediation runs inside the diligence window, in parallel with the rest of the technical review, because its findings move money at closing. After the transaction, the dossier joins the aircraft's permanent records so the reconstruction is done once, while the sources still exist, rather than repeated at every future sale.
Jurisdiction-specific considerations
Recordkeeping obligations under 14 CFR 91.417 and Regulation (EU) No 1321/2014 both presume continuity, and neither regime offers a formal mechanism that erases a gap. An aircraft that crossed registries during the silent period adds a complication and an opportunity: export certificates of airworthiness and registry filings from the transfer often become the best-dated independent evidence inside the gap.
Regulatory limits
The engagement documents what evidence exists for the gap period and states the confidence each conclusion deserves. Whether the aircraft is airworthy, and whether the buyer proceeds, are decisions this work informs but does not make, and no reconstruction substitutes for records a regulation requires.
What this review does not cover
- Physical inspection, borescope, or condition survey of the aircraft
- Valuation, appraisal, or deal structuring advice beyond the residual-risk statement
- Legal action or formal discovery against prior custodians
Specific to this review
- A gap during corroborated storage prices completely differently from a gap during operation, so proving which one it was is usually the highest-value hour of the whole engagement.
- Boundary arithmetic is the fastest lie detector available: if hours and cycles across the gap do not reconcile, no storage story survives it.
- Secondary sources decay on different clocks; flight-tracking archives, MRO job files, and insurance records each have retention horizons, and the deal that waits loses them in that order.
- Once a gap is dossiered and priced into one transaction, it stops being a surprise in the next, which is why buyers who remediate at acquisition recover the cost at exit.
Sources
U.S. Government (eCFR). Records an owner or operator must keep, including total time in service, current status of life-limited parts, and AD compliance.
U.S. Government (eCFR). Requirement to transfer maintenance records with an aircraft on sale or transfer of ownership.
Federal Aviation Administration. FAA guidance on making and keeping maintenance records and acceptable recordkeeping practices.
European Union / EASA. Continuing airworthiness, maintenance records, CAMO responsibilities, and the airworthiness review process in the EASA system.
Frequently asked questions
Can a logbook gap ever be fully cured?
The missing entries cannot be recreated, but the period can be accounted for. A gap backed by a dossier of independent, consistent evidence behaves in a transaction much like continuous records, because the buyer's question was never really about the pages; it was about what happened to the aircraft. Where the evidence stays thin, the honest outcome is a bounded risk statement, which is still worth more than an unexamined hole.
Relevant glossary terms
Related pages
Where this fits
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