Direct Answer
The most common FAA audit findings for Part 135 operators are documentation gaps, not unsafe flying: a manual (GOM/GMM) that is out of revision or was never distributed and acknowledged (14 CFR 135.21); incomplete or expired pilot qualification and training records (14 CFR 135.63); flight, duty, and rest records that cannot be reconstructed; and maintenance records with no entry, an inadequate description of the work, or a missing airworthiness-directive method-of-compliance entry (14 CFR 135.439).
Documentation gaps top the list because under Part 135 the record is the requirement — an inspector verifies compliance by reading the file, not by re-watching the flight or the maintenance task. The FAA does not publish a ranked percentage for any single finding type, so we frame this qualitatively from primary-source recordkeeping rules and published audit-preparation guidance. The operator who can produce any record on demand, the first time it is asked for, closes most findings before they open.
If you only have time to read one paragraph: the fastest way to fail a Part 135 surveillance event is not to fly badly — it is to be unable to prove you flew and maintained the aircraft correctly. This piece walks through the findings that recur most, ties each to the regulation that makes the record mandatory, and explains how the FAA decides between a coaching-style compliance action and formal enforcement. For the document-by-document request order an inspector typically works through, see our companion guide, how to prepare for a Part 135 FAA surveillance audit.
Why Documentation Gaps Top the List
There is a structural reason paperwork findings dominate Part 135 surveillance, and it is worth understanding before looking at the specific findings. The Part 135 recordkeeping regulations do not merely encourage good records — they make the record the legal object of the requirement. Three sections do most of the work:
Requires the certificate holder to prepare and keep current a manual setting forth its procedures and policies, acceptable to the Administrator, used by flight, ground, and maintenance personnel, with at least one copy at the principal base of operations. The requirement is the current, used, distributed manual — not just having good procedures in someone's head.
Requires a current list of aircraft, an individual record for each pilot (certificate, ratings, experience, current duties, medical class and date, competency test results, flight time), and individual flight-attendant records — with stated retention windows. The proof of a qualified, current crew lives entirely in these files.
Requires records of total time in service, life-limited part status, time since last overhaul of time-controlled items, current inspection status, and airworthiness-directive compliance status including date and method. A perfectly executed inspection with no log entry does not exist as far as the regulation is concerned.
Put those three together and a pattern emerges: every compliance area an inspector reviews ultimately resolves into a document. A pilot is current because a training record says so. An aircraft is airworthy because a maintenance entry says so. The operation is controlled because a manual and an aircraft list say so. When any of those documents is missing, stale, contradictory, or unretrievable, the underlying good practice becomes invisible — and an invisible compliance posture is, for audit purposes, a deficient one.
A note on statistics
You will see blog posts and vendors quote a precise figure — “X% of Part 135 findings are documentation gaps.” The FAA does not publish a public, ranked tally of Part 135 finding types, so we do not cite a percentage. What is well supported by primary-source rules and published audit-preparation guidance is the qualitative claim: documentation gaps are among the most common findings, and they are the failure mode that nearly every other compliance area can collapse into.
Related Part 135 records reading
The Part 135 Findings Operators See Most
Each finding below is grounded in the governing CFR (linked to Cornell Law's CFR text) and in widely published Part 135 audit-preparation guidance. They are ordered by how frequently they are described as recurring, not by any official FAA ranking — there is no public ranked list.
Manual not current — or revisions not distributed and acknowledged
14 CFR 135.2114 CFR 135.21 requires the certificate holder to prepare and keep current a manual setting forth its procedures and policies, acceptable to the Administrator, used by flight, ground, and maintenance personnel, with at least one copy at the principal base of operations. The most common manual finding is not that the manual is wrong — it is that the version in use is out of revision sync, or that a revision was made but never distributed to and acknowledged by the people who must follow it. Discrepancies between what the manual says and how the operation actually runs are a classic audit theme.
What the inspector is actually checking
General Operations Manual (GOM) — current revision on file at the base
Verify the shelf copy matches the accepted revision, with revision dates and a distribution/acknowledgment record for each required recipient.
General Maintenance Manual (GMM) — current revision
Maintenance procedures must be current and consistent with how maintenance is actually controlled and documented.
Internal consistency between manual, OpSpecs, and actual practice
Conflicting or stale procedures across documents raise oversight questions even when no single document is wrong on its own.
Incomplete or expired pilot qualification and training records
14 CFR 135.6314 CFR 135.63 requires the certificate holder to keep an individual record for each pilot, including certificate type and number, ratings, aeronautical experience, current duties, medical certificate class and date, competency test results, and flight time — and to retain those records. The recurring finding is a file that is missing a required element, or a training or check that has lapsed past its window. Because each pilot is a separate file with multiple time-sensitive elements, a single roster can generate several findings if currency is not actively surfaced.
What the inspector is actually checking
Per-pilot record: certificate, ratings, experience, current duties
The section enumerates what each individual pilot file must contain; a missing required element is a finding on its own.
Medical certificate — class and effective date recorded in the file
The record must capture the medical class and date; an expired or unrecorded medical surfaces immediately when the file is pulled.
Competency check and recurrent training records
Competency test results are part of the required pilot record; lapsed checks are among the most frequently cited per-pilot deficiencies.
Ground training records (initial, transition, upgrade)
Required ground instruction must be recorded; an undocumented training event is treated the same as a training event that never happened.
Flight, duty, and rest records that cannot be reconstructed
14 CFR 135.63Inconsistent or incomplete duty-and-rest tracking is one of the most frequently described compliance pitfalls in Part 135 operations. Flight time records are part of the per-pilot recordkeeping requirement under 14 CFR 135.63, and the section sets a 12-month retention floor for individual pilot records. The finding is rarely "the pilot flew illegally" — it is far more often "the operator cannot demonstrate from its records that the pilot flew legally," which under a record-based oversight system amounts to the same deficiency.
What the inspector is actually checking
Flight time records for each pilot
Captured per pilot and retained for at least 12 calendar months; gaps or contradictions are a finding.
Duty and rest documentation supporting flight/duty limits
Records must let an inspector reconstruct that applicable limitations were met for the operation conducted.
Load manifest — retained at the principal operations base
The section requires the load manifest to be kept at the principal operations base for at least 30 days.
Maintenance records: no entry, inadequate description, or wrong reference
14 CFR 135.43914 CFR 135.439 requires the certificate holder to keep maintenance records showing total time in service of the airframe, engine, propeller, and rotor; the current status of life-limited parts; time since last overhaul of items required to be overhauled on a time basis; the current inspection status; and the current status of applicable airworthiness directives, including the date and method of compliance. Published maintenance-documentation guidance repeatedly names the same defects: no documentation of the work, an inadequate description of what was done, and citing the wrong reference. Each of these turns completed, airworthy work into an unprovable claim.
What the inspector is actually checking
Total time in service — airframe, engine, propeller, rotor
A required record element; gaps undermine the entire airworthiness narrative for the aircraft.
Current inspection status against the inspection program
Must identify the current inspection status, including time since the last required inspections.
Life-limited part status and time since last overhaul
The current status of life-limited parts and overhaul intervals for time-controlled items must be tracked.
Airworthiness directive compliance — date and method
AD status must include the date and method of compliance; an applicable AD without a documented method-of-compliance entry is a finding even if the work was performed.
Unclear operational control, leasing, or recordkeeping availability
14 CFR 135.63Audit-preparation guidance for business aviation repeatedly flags unclear leasing or operational-control arrangements as a source of findings, and 14 CFR 135.63 requires the certificate holder to keep its required records at, or make them available at, its principal base of operations. A finding here can take two forms: the operational-control or lease paperwork does not clearly establish who holds operational control of a given flight, or the required records simply are not where, or as available as, the regulation requires when the inspector asks.
What the inspector is actually checking
Records kept at / available at the principal base of operations
If an inspector asks for a required record and it is not retrievable where the rule requires, that is a deficiency regardless of how the operation went.
Current list of aircraft used or available for use
The section requires a current aircraft list; a stale list after a fleet change is a common, easily avoided finding.
Operational-control / lease documentation clarity
Arrangements that blur who holds operational control of a flight invite questions; clear, current documentation closes them.
Find your documentation gaps before the inspector does
The free FAA Readiness Score walks the same record categories surveillance covers — manual currency, per-pilot files, duty/rest reconstructability, and maintenance entries — and flags where a gap is most likely to surface as a finding. No signup required; under 3 minutes.
Run the Free FAA Readiness ScoreHow Often the FAA Audits — and What Happens When It Finds a Gap
There is no fixed audit interval
One of the most-searched questions — “how often does the FAA audit a Part 135 operator?” — does not have a fixed-interval answer. The FAA oversees Part 135 certificate holders through the Safety Assurance System (SAS), which the FAA describes as a risk-based, data-supported oversight system that targets surveillance resources rather than running on a single calendar clock. SAS is the oversight framework for 14 CFR parts 121, 135, and 145; the FAA is explicit that it does not impose new requirements on certificate holders — it standardizes how inspectors evaluate the programs the regulations already require. In practical terms, an operator should expect ongoing surveillance whose timing and intensity flex with risk indicators: newly certificated status, recent findings, accidents or incidents, fleet or operations changes, key-personnel turnover, and OpSpec amendments. Ramp inspections and en-route observations can also happen without notice.
If someone promises you a fixed audit frequency, be skeptical
The public SAS model does not guarantee a predictable “every 12 months” visit. The safe operating assumption is continuous readiness — because an event-driven assessment pulls the same record categories as a planned one. An operator who is only ready in the weeks before an expected visit is exposed the rest of the year.
A finding is not automatically an enforcement case
What happens after a finding is governed by the FAA Compliance Program (FAA Order 8000.373). The FAA states that many deviations arise from flawed procedures, simple mistakes, lack of understanding, or diminished skills, and that these are often most effectively corrected through root-cause analysis and improvements to procedures or training — a compliance action rather than legal enforcement. The same program is equally clear that reluctance or failure to correct, or repeated deviations, may result in enforcement. So the determining factor is rarely the existence of a single documentation gap; it is how the operator responds and whether the same gap keeps recurring.
Tends toward a compliance action
- First-time, openly disclosed documentation gap
- Root cause identified and procedures/training improved
- Correction is prompt and verifiable in the records
- No pattern of the same deficiency across cycles
Tends toward enforcement
- Reluctance or failure to correct the deficiency
- Repeated deviations across surveillance events
- Conduct beyond a simple, correctable mistake
- Inability to demonstrate the root cause was addressed
The strategic implication is clean: the way to stay in the compliance-action lane is to make findings rare and corrections fast and verifiable. Both are records problems. An operator whose system surfaces an expiring training check 60 days out never produces the finding; an operator who can attach a corrected entry to a root-cause memo the same week demonstrates exactly the responsiveness the Compliance Program rewards.
Closing the Documentation Gaps Before They Become Findings
Because the most common findings are documentation gaps, the highest-leverage compliance work an operator can do is not memorizing the CFR — it is making every required record current, complete, and retrievable on demand. Four habits eliminate most of the findings above.
Treat the manual as a living, distributed document
Keep the GOM and GMM in revision sync with the accepted version, and maintain a distribution-and-acknowledgment record so you can show every required recipient received the current revision. Most manual findings are distribution gaps, not content errors.
Surface expiring records before they lapse
Every medical, competency check, recurrent training event, and equipment inspection has a window. A system that flags items at 90, 60, and 30 days converts the single most common per-pilot and per-aircraft finding into a non-event.
Make duty/rest reconstructable, not just compliant
It is not enough to fly legally — the records must let an inspector reconstruct that you did. Keep flight-time records complete and retained for the required window, with the supporting duty/rest data available at the principal base.
Never let work outrun its log entry
For maintenance, the entry is the work as far as the regulation is concerned. Capture an adequate description of the task, the correct reference, and — for any applicable AD — the date and method of compliance, every time, before the record can drift.
FileFlo: the proof layer aimed directly at the top of the findings list
FileFlo is a compliance document intelligence platform — a proof layer that sits alongside your existing stack (flight scheduling, maintenance tracking, training software) and makes the records those systems produce current, complete, and instantly retrievable. It does not conduct your audit, represent you to the FAA, give legal advice, or replace your safety management system, dispatch/FOS, or maintenance-tracking platform. What it does is classify documents against the governing CFR, track expiration windows on every medical, training check, and equipment inspection, flag missing or stale manual revisions and missing maintenance entries, and assemble an inspector-ready package across the company, pilot, and aircraft layers on demand.
Since the most common Part 135 findings are documentation gaps — stale manuals, incomplete pilot records, unreconstructable duty/rest, and missing maintenance entries — a system whose entire job is to eliminate documentation gaps is pointed straight at the problem. The objective is simple and concrete: be able to produce any record an inspector asks for, on demand, the first time.
Keep reading — Part 135 audit-prep & records
Frequently Asked Questions
What are the most common FAA audit findings for Part 135 operators?
Across Part 135 surveillance, the findings that recur most are documentation problems rather than unsafe flying. The patterns FAA inspectors and aviation auditors repeatedly describe include: a manual (GOM/GMM) that is not current or whose revisions were not distributed and acknowledged; incomplete or expired pilot training and check records; flight, duty, and rest records that are inconsistent or cannot be reconstructed; unclear operational-control or aircraft-leasing arrangements; and maintenance records that have no entry, an inadequate description of the work performed, or the wrong reference. The common thread is that the work may have been done correctly, but the record that proves it is missing, stale, or contradictory. Because the underlying regulations — 14 CFR 135.21, 135.63, and 135.439 — make the record itself the requirement, a documentation gap is a finding even when the flying and the wrenching were sound. FileFlo does not assert a fixed percentage for any single finding type because the FAA does not publish a public ranked tally; we frame this qualitatively from primary-source recordkeeping rules and published audit-preparation guidance.
Why do documentation gaps top the list of FAA findings?
Because under Part 135 the document is the deliverable. 14 CFR 135.21 requires the certificate holder to prepare and keep a manual current and acceptable to the Administrator; 14 CFR 135.63 requires individual pilot records and a current aircraft list, with stated retention windows; and 14 CFR 135.439 requires maintenance records showing total time in service, life-limited part status, inspection status, and airworthiness directive compliance. An inspector cannot verify compliance by watching a flight or a maintenance task that already happened — they verify it by reading the record. So a perfectly flown trip with an unrecorded duty period, or a properly completed inspection with no log entry, both become findings. Documentation gaps top the list because they are the one failure mode that every other compliance area can collapse into: a missing signature, an out-of-date revision, or an unretrievable file converts good operational practice into a paperwork violation.
How often does the FAA audit a Part 135 operator?
There is no fixed public interval such as "every N months." The FAA oversees Part 135 certificate holders through the Safety Assurance System (SAS), which the FAA describes as a risk-based, data-supported oversight system that targets surveillance resources rather than running on a single calendar clock. In practice, an operator can expect ongoing surveillance activity, with timing and intensity influenced by risk indicators — newly certificated status, recent findings, accidents or incidents, fleet or operations changes, key personnel turnover, and OpSpec amendments. Inspectors can also conduct ramp inspections and en-route observations without advance notice. The practical takeaway: treat readiness as continuous rather than assuming a predictable annual visit, because an event-driven assessment pulls the same record categories as a planned one. Anyone who quotes you a guaranteed fixed audit frequency is describing something the public SAS model does not promise.
What records does an FAA inspector ask for first in a Part 135 audit?
Inspectors generally begin at the company level to confirm the operator is authorized and its governing program is current: the Air Carrier Certificate, current Operations Specifications, and the General Operations Manual under 14 CFR 135.21 (including revision history and distribution acknowledgments). From there, surveillance typically moves to per-pilot qualification and currency records under 14 CFR 135.63 — airman and medical certificates, competency and proficiency checks, line checks, and recurrent training — and then to per-aircraft airworthiness and maintenance records under 14 CFR 135.439, including total time in service, current inspection status, life-limited part status, and airworthiness directive compliance. The exact sequence varies by the inspector and the scope of the assessment, but the manual-then-people-then-aircraft pattern is what most published Part 135 audit-preparation guidance describes.
What happens when the FAA finds a documentation deficiency?
Not every finding becomes an enforcement case. Under the FAA Compliance Program (FAA Order 8000.373), the agency states that many deviations stem from flawed procedures, simple mistakes, lack of understanding, or diminished skills, and that these are often most effectively corrected through root-cause analysis and improvements to procedures or training — a compliance action rather than legal enforcement. The FAA also states that reluctance or failure to correct, or repeated deviations, may lead to enforcement. So a first-time, openly disclosed documentation gap that the operator fixes at the root cause is treated very differently from the same gap left uncorrected or repeated across surveillance cycles. The reliable way to stay in the compliance-action lane is to make findings rare and corrections fast and verifiable — which is fundamentally a records-management problem.
How long must a Part 135 operator keep pilot and maintenance records?
Under 14 CFR 135.63, the certificate holder keeps individual pilot records, and the section sets retention windows: pilot records are retained for at least 12 calendar months, the aircraft-related records the section calls out are kept for at least 6 calendar months, and a load manifest is kept at the principal operations base for at least 30 days. Maintenance records under 14 CFR 135.439 follow a dual scheme: routine records are retained until the work is repeated or superseded, or for one year after the work is performed, while the records that establish life-limited part status, total time in service, current inspection status, and airworthiness directive compliance are kept and transferred with the aircraft when it is sold. A retention miss is its own finding — an inspector who asks for a record inside its required window and is told it was discarded has documented a deficiency regardless of how the underlying operation went.
Are most FAA findings about safety or about paperwork?
In the Part 135 surveillance context, the recurring findings are overwhelmingly about the record, not the act. That does not make them trivial — the FAA treats the record as the proof of safety, so a documentation gap is treated as a real compliance deficiency. But it does mean the fix is usually administrative rather than operational: distribute and acknowledge a manual revision, capture a duty period that was actually flown legally, log an inspection that was actually performed, attach the airworthiness directive method-of-compliance entry to work that was actually done. Operators who internalize that "the record is the requirement" stop treating documentation as after-the-fact bookkeeping and start treating it as part of the operation itself — which is exactly where the most common findings disappear.
How does FileFlo help close documentation gaps before an FAA audit?
FileFlo is a compliance document intelligence platform — the proof layer. It does not conduct your audit, represent you to the FAA, or provide legal advice, and it is not your safety management system, dispatch/FOS, or maintenance-tracking platform. What it does is make the records those systems produce current, complete, and instantly retrievable: it classifies documents against the governing CFR, tracks expiration windows on medicals, training checks, and equipment inspections so nothing lapses unnoticed, flags missing or stale manual revisions and missing maintenance entries, and assembles an inspector-ready package across the company, pilot, and aircraft layers on demand. Because the most common findings are documentation gaps, a system whose entire job is to eliminate documentation gaps is aimed directly at the top of the findings list. The goal is simple: be able to produce any record an inspector asks for, on demand, the first time.
The most common finding is the one you can prevent with better records
FileFlo tracks every document across the three surveillance domains — company certificate and manual, per-pilot currency, and per-aircraft airworthiness — surfaces anything approaching its window, and produces an inspector-ready package on demand. Starter plan at $89/month. Professional at $299/month (unlimited pilots and aircraft). Five-day free trial, no credit card required.
5-day free trial · No credit card required · Cancel anytime · FileFlo is the compliance proof layer — it does not conduct your audit, represent you to the FAA, or replace your SMS, dispatch, or maintenance-tracking system.