Ask two Part 135 directors of maintenance what program governs their aircraft and you can get two different answers — sometimes for the same airframe. The confusion is understandable: 14 CFR Part 135 Subpart J reads as a wall of cross-referenced section numbers, the working terms operators actually use ("CAMP," "AAIP," "CASS") do not all appear verbatim in the regulation, and the single most-cited section for the "continuing analysis and surveillance" requirement is frequently cited to the wrong section.
This guide untangles all of it. We start with the line that decides everything — the type-certificated passenger seating threshold in 14 CFR §135.411 — then walk the 10-or-more-seat continuous-airworthiness program (the "CAMP"), the §135.431 Continuing Analysis and Surveillance System, the two record categories and retention periods in §135.439, and the §135.443 airworthiness release that returns the aircraft to service.
If you want the master index of every Part 135 record — pilot files, drug-and-alcohol, training, SMS — start with What Records Must a Part 135 Operator Keep and treat this as the maintenance-records deep dive.
Part 135 Maintenance Runs on Two Tracks
14 CFR §135.411(a) does something deceptively simple: it sorts every Part 135 aircraft into one of two maintenance regimes based on the aircraft's type-certificated passenger seating configuration, excluding any pilot seat. Everything downstream — what inspection program applies, whether you need a CASS, what records §135.439 obligates, who can sign the return to service — flows from which side of that line your aircraft sits on.
| Dimension | 9 Seats or Fewer §135.411(a)(1) | 10 Seats or More §135.411(a)(2) |
|---|---|---|
| Governing sections | Parts 91 & 43 + §§135.415, 135.417, 135.421, 135.422 | §§135.415, 135.417, and 135.423 through 135.443 |
| Working term | Part 91/43 baseline (optional AAIP) | CAMP (continuous-airworthiness maintenance program) |
| Inspection program | Part 91 inspections, or AAIP under §135.419 | Inspection program in the manual (§135.427) |
| CASS required? | No (unless the operator elects the §135.411(a)(2) program under §135.411(b)) | Yes — §135.431 |
| Required inspection items (RII) | Not required as such | Designated in manual under §135.427(b)(2) |
| Records rule | §91.417 (+ §135.421 for engine trend data) | §135.439 |
| Return to service | §43.9 / §43.11 entry | §135.443 airworthiness release |
"CAMP" Is a Term of Art — the CFR Describes It by Its Sections
You will not find the literal acronym "CAMP" defined in §135.411. The regulation says aircraft of 10 seats or more "shall be maintained under a maintenance program in §§135.415, 135.417, 135.423 through 135.443." The industry — and FAA guidance — refer to that bundled program as a Continuous Airworthiness Maintenance Program, or CAMP. Part 91 uses a parallel concept in §91.409(f)(1) when it lets large airplanes, multiengine turbojet and turboprop airplanes, and turbine-powered rotorcraft adopt "a continuous airworthiness inspection program" used by a Part 121 or 135 carrier. When this guide says "CAMP," read it as shorthand for the §§135.423–135.443 program.
The 9-vs-10-Seat Line — 14 CFR §135.411
The threshold is measured by type-certificated passenger seating configuration, excluding any pilot seat — not by how many seats are physically installed today, and not by how many passengers you actually carry. A nine-passenger aircraft is a nine-passenger aircraft for §135.411 purposes even if you fly it with two empty seats.
Nine Seats or Fewer — §135.411(a)(1)
Aircraft type certificated for a passenger seating configuration of nine seats or fewer (excluding any pilot seat) "shall be maintained under parts 91 and 43 of this chapter and §§135.415, 135.417, 135.421 and 135.422." In plain terms: you maintain and inspect the aircraft to the Part 91 standard (annual / 100-hour or an approved program), you keep records under §91.417, you file service difficulty reports under §135.415, and you carry the additional maintenance obligations of §135.421. As an option, §135.411(a)(1) lets you instead use an Approved Aircraft Inspection Program (AAIP) under §135.419.
Ten Seats or More — §135.411(a)(2)
Aircraft type certificated for a passenger seating configuration of 10 seats or more (excluding any pilot seat) "shall be maintained under a maintenance program in §§135.415, 135.417, 135.423 through 135.443." This is the full continuous-airworthiness maintenance program — the CAMP. It pulls in a maintenance organization (§135.423), the maintenance manual and required inspection items (§135.427), the continuing analysis and surveillance system (§135.431), the recordkeeping requirements (§135.439), and the airworthiness release (§135.443), among others. This track is materially more demanding than the Part 91 baseline.
The AAIP is the bridge — and §135.419 has its own requirements
An AAIP under §135.419 is not a paperwork shortcut. The Administrator may require one whenever the part 91 inspections are not adequate, or a certificate holder may apply for one. The program must contain detailed inspection instructions and procedures covering the airframe, engines, propellers, rotors, and appliances; a schedule expressed in time in service, calendar time, or number of system operations; and procedures for recording discrepancies and their correction or deferral. Once approved, the certificate holder must include the AAIP in the manual required by §135.21, and each aircraft's registration number must be listed in the operations specifications.
§135.421 — the extra duties nine-or-fewer operators owe
Even on the Part 91/43 track, §135.421 adds obligations that generate records:
- For each aircraft engine, propeller, rotor, and each item of required emergency equipment, the operator must comply with the manufacturer's recommended maintenance programs, or a program approved by the Administrator.
- Single-engine aircraft used to carry passengers in IFR operations must follow an engine trend monitoring program — including an oil analysis where appropriate — and must keep the results of each test, observation, and inspection.
Inside the CAMP — §§135.423 through 135.443
For 10-or-more-seat aircraft, §135.411(a)(2) builds the maintenance program out of the §§135.423–135.443 block. Three of those sections do the heavy lifting for the program's structure; §135.439 (records) and §135.443 (release) get their own sections below.
§135.423 — Maintenance Organization
A certificate holder that performs any of its own maintenance, preventive maintenance, or alterations — or that performs required inspections — "must have an organization adequate to perform that work." Critically, §135.423(c) requires that whenever required inspections and other maintenance are performed by the same organization, the certificate holder must organize the work so as to separate the required-inspection functions from the other maintenance functions. That separation is itself documented in the manual.
§135.427 — Manual Requirements and Required Inspection Items
This is the section most often miscited as the CASS rule. It is not. §135.427 is titled "Manual requirements." It requires the certificate holder to put the maintenance programs into the manual and to designate, among other things: the method of performing routine and non-routine maintenance other than required inspections (§135.427(b)(1)); the required inspection items (RII) — the items of maintenance and alteration that must be inspected because doing them improperly could endanger safe operation (§135.427(b)(2)); and the method of performing required inspections plus the occupational titles of personnel authorized to perform each (§135.427(b)(3)).
Service Difficulty Reports — §135.415
Both tracks share one reporting obligation: §135.415 requires the certificate holder to report each failure, malfunction, or defect of the kind listed in the rule. Reports of occurrences during a 24-hour period are submitted to the FAA collection point within the next 96 hours (with weekend/holiday occurrences allowed to roll to the next workday). The SDR is a record in its own right — and the underlying discrepancy will usually also appear in the maintenance log and feed the §135.431 CASS.
CASS — Continuing Analysis and Surveillance, 14 CFR §135.431
The Continuing Analysis and Surveillance System is the closed-loop quality function of a 10-or-more-seat program. It is the part of the maintenance program that watches the maintenance program. And it lives in §135.431 — titled, in the CFR, "Continuing analysis and surveillance."
What §135.431(a) Actually Requires
Each certificate holder must "establish and maintain a system for the continuing analysis and surveillance of the performance and effectiveness of its inspection program and the program covering other maintenance, preventive maintenance, and alterations and for the correction of any deficiency in those programs, regardless of whether those programs are carried out by the certificate holder or by another person."
§135.431(b) lets the Administrator, on finding the programs do not contain adequate procedures and standards to meet the requirements of Part 135, require the certificate holder to make changes after receiving notice. §135.431(c) gives the certificate holder 30 days to petition the Administrator to reconsider that change notice; filing the petition stays the change pending a decision, except in the case of an emergency requiring immediate action in the interest of safety.
The contracted-out trap: "regardless of whether... carried out by another person"
If a 10-or-more-seat operator contracts its heavy maintenance to a Part 145 repair station, the §135.431 CASS obligation does not transfer with the work. The certificate holder remains responsible for the continuing analysis and surveillance of that contracted maintenance and for correcting deficiencies in it. The CASS records — audit findings, trend analyses, and the corrective actions that closed them — are exactly what an FAA Principal Maintenance Inspector looks for during a SAS surveillance visit.
Maintenance Recordkeeping — 14 CFR §135.439
For the 10-or-more-seat program, §135.439 is the maintenance-records rule. It divides the records into two categories with two different retention regimes — and getting the categories straight is the difference between a clean records review and a finding.
"All the records necessary to show that all requirements for the issuance of an airworthiness release under §135.443 have been met." In practice: the work orders, inspection sign-offs, parts traceability, and entries that substantiate each return to service.
The aircraft's ongoing status set — total time in service, life-limited part status, time since overhaul, current inspection status, AD status, and the list of major alterations and repairs. These are the records that prove where the aircraft stands today.
The §135.439(a)(2) status records, item by item
- The total time in service of the airframe, each engine, each propeller, and each rotor.
- The current status of life-limited parts of each airframe, engine, propeller, rotor, and appliance.
- The time since last overhaul of each item installed on the aircraft that is required to be overhauled on a specified time basis.
- The identification of the current inspection status of the aircraft, including the times since the last inspections required by the inspection program under which the aircraft and its appliances are maintained.
- The current status of applicable airworthiness directives, including the date and methods of compliance — and, for recurring ADs, the time and date when the next action is required.
- A list of current major alterations and repairs to each airframe, engine, propeller, rotor, and appliance.
| Record | Retention Period | Authority |
|---|---|---|
| Release-support records (a)(1) | Until the work is repeated or superseded, or 1 year after the work is performed | §135.439(b)(1) |
| Last complete overhaul records | Until superseded by work of equivalent scope and detail | §135.439(b)(2) |
| Status records (a)(2) | Retained and transferred with the aircraft at the time the aircraft is sold | §135.439(b)(3) |
§135.439 mirrors the §91.417 baseline — don't confuse the retention numbers
The §135.439 structure deliberately parallels the Part 91 records rule in §91.417: routine maintenance records are kept until repeated or superseded, or for one year; status records (total time, life-limited parts, AD status, inspection status, major alterations and repairs) follow the aircraft and transfer to the buyer on sale. A common drafting error is to attach the "1 year" figure to the wrong records — the one-year floor is for the release-support / routine records, not for the status records, which are effectively life-of-aircraft. Note also that the "24 months" you may remember from aviation maintenance is the §91.411 / §91.413 altimeter-and-transponder test interval — it is not a records-retention period.
The Airworthiness Release — 14 CFR §135.443
The §135.439(a)(1) records exist to substantiate one thing: the §135.443 airworthiness release. This is the document — or maintenance-log entry — that legally returns a 10-or-more-seat aircraft to service after maintenance, preventive maintenance, or alterations.
What the §135.443 release must certify
No certificate holder may operate the aircraft after the work unless a person authorized under §135.443 prepares an airworthiness release or makes an entry in the aircraft maintenance log certifying, in substance, that:
- The work was performed in accordance with the requirements of the certificate holder's manual.
- All items required to be inspected were inspected by an authorized person who determined the work was satisfactorily completed.
- No known condition exists that would make the aircraft unairworthy.
- So far as the work performed is concerned, the aircraft is in condition for safe operation.
Who signs it
The release or log entry must be signed by an authorized certificated mechanic or repairman; a repairman may sign only for the work for which they are employed and certificated. For maintenance performed outside the United States, an authorized representative of an appropriately certificated repair station may sign. The certificate holder may also state in its manual that the signature of an authorized certificated mechanic or repairman constitutes the required certification. Personnel authorized to perform each required inspection are designated by occupational title in the manual under §135.427(b)(3); under §135.427(a), the manual must list the outside persons with whom the certificate holder has arranged to perform any of its required inspections, other maintenance, preventive maintenance, or alterations.
How it connects to §43.9
The maintenance-log entry that accompanies a release still has to satisfy the underlying Part 43 content rules. Our §43.9 maintenance-record entry guide breaks down the required elements — description of work, date completed, name of the person performing the work, and the signature, certificate number, and kind of certificate of the person approving the return to service. A release backed by an entry that is missing the certificate number or the kind of certificate is a records defect even if the work was done correctly.
The Maintenance Records You Must Be Able to Produce
Pulling the threads together, here is the maintenance-record set a 10-or-more-seat Part 135 operator must keep current and be able to produce on demand — each mapped to its governing section.
Airworthiness releases + support records
Every §135.443 release and the §135.439(a)(1) records (work orders, inspection sign-offs, parts traceability) that substantiate it. Retained 1 year / until superseded.
Status records
The §135.439(a)(2) set — total time in service, life-limited parts, time since overhaul, current inspection status, AD status, major alterations and repairs. Transfer with the aircraft on sale.
CASS records
The §135.431 continuing-analysis audit findings, trend data, and corrective actions — including for contracted-out maintenance.
Manual + RII designations
The §135.427 manual content: maintenance methods, the required inspection items, and the personnel authorized to perform each required inspection.
Service difficulty reports
The §135.415 reports of failures, malfunctions, and defects — filed within 96 hours of the 24-hour reporting period.
AD compliance records
Date and methods of compliance, plus recurring-AD next-due — the §135.439(a)(2) AD line, cross-referenced to the logbook entries.
For the AD piece specifically — the most commonly mis-documented status record — see How to Document AD Compliance So It Survives a Ramp Check. For the full cross-vertical recordkeeping master list, see What Records Must a Part 135 Operator Keep. And if any of your aircraft are maintained on the Part 91/43 baseline rather than a CAMP, the Part 91 aircraft-records guide covers the §91.417 framework that applies to them.
Keep every §135.439 maintenance record audit-ready
FileFlo is a compliance document intelligence platform — a read-only proof layer that classifies and tracks the records your maintenance program produces. It does not run your CAMP, your CASS, or your maintenance-tracking system, and it makes no live connection to them. You upload the documents; FileFlo:
- Classifies each document against the governing CFR (§135.439, §135.443, §135.431, §135.415, §91.417)
- Extracts dates and statuses and tracks expirations — AD next-due, inspection status, life-limited part timelines
- Sends 90/60/30-day expiration alerts before a recurring AD or inspection lapses — not the day after
- Generates an audit-ready maintenance-records binder organized by section for an FAA surveillance visit or a pre-purchase review
FileFlo sits alongside your Director of Maintenance, your A&P/IA, and your Part 145 repair station — it keeps the documents that prove your compliance, it does not perform or sign off maintenance. Starter $89/mo · Professional $299/mo · 5-day free trial, no credit card required.
Related Aviation Recordkeeping Guides
Frequently Asked Questions
What is the difference between a CAMP and an AAIP under Part 135?
They are two different ways to satisfy the inspection and maintenance obligation, and which one applies turns on the aircraft's type-certificated passenger seating configuration. Under 14 CFR §135.411(a)(2), aircraft type certificated for a passenger seating configuration of 10 seats or more (excluding any pilot seat) must be maintained under the full continuous-airworthiness maintenance program built from §§135.415, 135.417, and 135.423 through 135.443 — the set the industry calls a "CAMP." Under §135.411(a)(1), aircraft type certificated for nine seats or fewer (excluding any pilot seat) are maintained under parts 91 and 43 plus §§135.415, 135.417, 135.421, and 135.422 — but a nine-or-fewer operator may instead elect an Approved Aircraft Inspection Program (AAIP) under §135.419. So the short version: 10+ seats = mandatory CAMP-style program; nine-or-fewer = parts 91/43 baseline, with an optional AAIP. "CAMP" is the working term for the §§135.423–135.443 program; the CFR itself describes it by its component sections rather than by the acronym.
Does 14 CFR §135.427 require a CASS?
No — that is one of the most common citation mistakes in Part 135 maintenance. The Continuing Analysis and Surveillance System (CASS) requirement lives in 14 CFR §135.431, titled "Continuing analysis and surveillance." Section 135.431(a) requires each certificate holder to "establish and maintain a system for the continuing analysis and surveillance of the performance and effectiveness of its inspection program and the program covering other maintenance, preventive maintenance, and alterations and for the correction of any deficiency in those programs, regardless of whether those programs are carried out by the certificate holder or by another person." Section 135.427 is titled "Manual requirements" — it governs what the certificate holder must put in its manual, including the designation of required inspection items (RII) under §135.427(b)(2). Both sections belong to the 10-or-more-seat program, but only §135.431 is the CASS.
What records does 14 CFR §135.439 actually require an operator to keep?
14 CFR §135.439(a) requires the certificate holder to keep two categories of records. Category (a)(1) is all the records necessary to show that all requirements for the issuance of an airworthiness release under §135.443 have been met. Category (a)(2) is a records set that includes: the total time in service of the airframe, each engine, each propeller, and each rotor; the current status of life-limited parts of each airframe, engine, propeller, rotor, and appliance; the time since last overhaul of each item installed on the aircraft that must be overhauled on a specified time basis; the identification of the current inspection status of the aircraft, including the times since the last inspections required by the inspection program; the current status of applicable airworthiness directives, including the date and methods of compliance (and, for recurring ADs, the time and date when the next action is required); and a list of current major alterations and repairs to each airframe, engine, propeller, rotor, and appliance.
How long must Part 135 maintenance records be retained under §135.439?
The retention periods differ by record category. Under 14 CFR §135.439(b)(1), the §135.439(a)(1) records — those that show the airworthiness release requirements were met — must be retained for one year after the work is performed, or until the work is repeated or superseded by other work, whichever comes first. Under §135.439(b)(2), the records of the last complete overhaul of each item must be retained until the work is superseded by work of equivalent scope and detail. Under §135.439(b)(3), the §135.439(a)(2) records — total time in service, life-limited part status, AD status, current inspection status, and the list of major alterations and repairs — must be retained and transferred with the aircraft at the time the aircraft is sold. This mirrors the Part 91 baseline in §91.417: routine work has a one-year floor; the status records follow the aircraft for its service life.
What is the role of the airworthiness release under §135.443?
The airworthiness release is the single document that legally returns the aircraft to service after maintenance, preventive maintenance, or alterations under a 10-or-more-seat program. 14 CFR §135.443(a) prohibits operating an aircraft after such work unless the certificate holder prepares an airworthiness release, or makes an entry in the aircraft maintenance log; under §135.443(b)(3), that release or log entry must be signed by an authorized certificated mechanic or repairman. The release must certify, in substance, that the work was performed in accordance with the certificate holder's manual, that all items required to be inspected were inspected and found satisfactory, that no known condition exists that would make the aircraft unairworthy, and that the aircraft is in condition for safe operation. The §135.439(a)(1) records the operator must keep are precisely the records that substantiate each airworthiness release — which is why the recordkeeping requirement and the release requirement are joined at the hip.
Are nine-or-fewer-seat Part 135 operators exempt from maintenance recordkeeping?
No. A nine-or-fewer-seat operator maintained under §135.411(a)(1) follows parts 91 and 43, which carry their own recordkeeping obligations — principally the §91.417 maintenance-records rule and the §43.9 and §43.11 entry-content rules. They are not subject to the §135.423–135.443 program (including §135.439 and §135.443) unless they elect to maintain under the §135.411(a)(2) program (permitted by §135.411(b)). In addition, §135.421 imposes its own documentation duties: the certificate holder must comply with the manufacturer's recommended maintenance programs or an FAA-approved program for each aircraft engine, propeller, rotor, and each item of required emergency equipment, and single-engine aircraft used in IFR passenger operations must follow an engine trend monitoring program — including oil analysis where appropriate — and keep the results of each test, observation, and inspection. So the records framework is different, but it is not lighter in any way that an operator can afford to ignore.
Does the 2024 FAA SMS rule change Part 135 maintenance recordkeeping?
The 2024 SMS final rule does not rewrite the §135.439 maintenance-recordkeeping requirement, but it adds an adjacent records stream that every Part 135 operator must build. The rule requires all Part 135 certificate holders — with no aircraft-count threshold — to implement a Safety Management System under 14 CFR Part 5 by May 28, 2027. An SMS generates its own evidence: hazard reports, risk assessments, safety policy and accountable-executive documentation, safety assurance audit findings, and corrective-action records. Those records sit alongside the maintenance record set rather than replacing it, and the safety-assurance component of an SMS overlaps conceptually with the §135.431 CASS — both are continuous feedback loops on program effectiveness. We cover the SMS records in detail in a separate guide.
Who can sign a Part 135 airworthiness release?
Under 14 CFR §135.443(b)(3), the airworthiness release or maintenance-log entry must be signed by an authorized certificated mechanic or repairman. A repairman may sign only for the work for which they are employed and certificated. For maintenance performed outside the United States, the release may be signed by an authorized representative of an appropriately certificated repair station. The certificate holder may also establish, in its manual, that the signature of an authorized certificated mechanic or repairman constitutes the required certification. Personnel authorized to perform each required inspection are designated by occupational title in the manual under §135.427(b)(3); §135.427(a) requires the manual to list the outside persons with whom the certificate holder has arranged to perform any of its required inspections, other maintenance, preventive maintenance, or alterations — and the organization performing that work must be adequate under §135.423.
More Part 135 & Aviation Compliance Guides
What Records Must a Part 135 Operator Keep
The master index: every Part 135 record mapped to its CFR cite, owner, and retention period
Part 135 Pilot Records Required by the FAA
Per-crewmember file contents under §135.63(a)(4), §135.293, §135.297, and §135.299
Part 135 Drug & Alcohol Program Records
14 CFR Part 120 and 49 CFR Part 40 recordkeeping checklist for the D&A program
What Is Operational Control in Part 135
How 14 CFR §1.1 and §135.77 define operational control — and the documents that prove it
Prepare for a Part 135 FAA Surveillance Audit
The documents an FAA inspector requests during a SAS surveillance visit, in order
FAA Part 135 SMS 2027 Deadline
The Part 5 Safety Management System rule — applies to all Part 135 by May 28, 2027
Document AD Compliance for a Ramp Check
Logbook wording, recurring-AD next-due math, and §91.417(a)(2)(v) retention
What a §43.9 Maintenance Entry Must Contain
The 5 required elements of every compliant aviation maintenance record entry
Part 91.409 Inspection Requirements
Annual, 100-hour, progressive, and AAIP — who signs each and what records they produce
Part 91 Aircraft Records Requirements
The §91.417 framework that applies to nine-or-fewer-seat aircraft on the Part 91/43 track
The Part 145 Audit Binder
Every document an FAA inspector asks for during a Part 145 surveillance visit, in order
Part 145 Repair Station Recordkeeping
What §145.219 demands of the repair stations that perform your contracted maintenance
Prove your Part 135 maintenance records before the FAA asks
FileFlo classifies your maintenance records against 14 CFR §135.439, §135.443, §135.431, and §135.415, extracts AD and inspection due dates, and sends 90/60/30-day alerts before any recurring item lapses. Keep every airworthiness release, status record, CASS finding, and SDR documented and organized by CFR section — ready for a surveillance visit or a pre-purchase review.
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