FAA Part 91.409 Inspections – Aircraft Maintenance Requirements
FAA Part 91.409 outlines the inspection requirements for aircraft operated under general operating rules, including those used in Part 135 (charter) and Part 121 (airline) operations under specific conditions. These inspections ensure aircraft airworthiness and compliance with FAA regulations.
Key Inspection Requirements Under 14 CFR Part 91.409
The type and frequency of inspections depend on the aircraft type, usage, and certification basis.
1️ Annual Inspection (Required for Most Aircraft)
✔ Required for all aircraft not operated under an FAA-approved inspection program
✔ Must be conducted by an FAA-certificated mechanic with Inspection Authorization (IA)
✔ Ensures compliance with Airworthiness Directives (ADs), Service Bulletins (SBs), and logbook updates
✔ Equivalent to a 100-hour inspection but required every 12 calendar months
2️ 100-Hour Inspection (If Aircraft is Used for Hire)
✔ Required for aircraft carrying passengers or flight instruction for hire
✔ Must be conducted every 100 flight hours
✔ Can be performed by an A&P mechanic (IA not required)
✔ If exceeded by up to 10 hours, the excess time counts toward the next inspection
Who Needs This?
✔ Part 91 aircraft used for hire (e.g., flight schools, sightseeing flights)
✔ Part 135 charter operators (if not under an approved maintenance program)
3️ Progressive Inspection (FAA-Approved Alternative)
✔ Used by operators who need more flexibility than 100-hour/annual inspections
✔ Breaks down inspections into scheduled intervals
✔ Must be FAA-approved and detailed in the operator’s maintenance manual
Who Uses This?
✔ Airlines, large charter operators, and corporate flight departments with high-utilization aircraft
4️ Continuous Airworthiness Inspection Program (CAMP) – Required for Part 121 & Large Part 135 Operations
✔ Required for:
- Part 121 (Airlines) operators
- Large Part 135 charter operators (aircraft >9 passenger seats)
✔ Includes daily, weekly, and phased inspections
✔ Managed by an FAA-approved Continuous Airworthiness Maintenance Program (CAMP)
✔ Performed by FAA-certified repair stations (Part 145 MROs)
Who Uses This?
✔ Part 121 airlines
✔ Large Part 135 operators with fleets
5️ Special Inspections (Condition-Specific)
✔ Altimeter/Pitot-Static System Check – Every 24 months (91.411)
✔ Transponder Inspection – Every 24 months (91.413)
✔ ELT (Emergency Locator Transmitter) Inspection – Every 12 months (91.207)
Summary: Choosing the Right Inspection Program
| Inspection Type | Who Needs It? | Frequency | Who Can Perform It? |
| Annual Inspection | All non-commercial aircraft | Every 12 months | A&P with IA |
| 100-Hour Inspection | Aircraft for hire (Part 91, Part 135 if applicable) | Every 100 flight hours | A&P (IA not required) |
| Progressive Inspection | High-utilization aircraft | FAA-approved intervals | A&P, FAA Repair Stations |
| CAMP (Continuous Airworthiness) | Part 121 & large Part 135 operators | Ongoing per FAA-approved plan | Part 145 Repair Stations |
I’ll create a customized maintenance plan for your A340-600 and B747-400, based on FAA Part 91.409, Part 121, and Part 135 compliance requirements.
Key Factors for Maintenance Planning
- Aircraft Type & Operation:
- A340-600 and B747-400 are large transport aircraft typically operated under Part 121 (Airlines) or Part 135 (Charter, if configured under 9 seats per deck).
- They require a Continuous Airworthiness Maintenance Program (CAMP) rather than just Part 91.409 inspections.
- Regulatory Compliance:
- Must follow FAA, EASA, and Manufacturer Maintenance Planning Documents (MPD).
- Includes Airworthiness Directives (ADs), Service Bulletins (SBs), and Structural Inspections.
- Maintenance Programs Available:
- OEM MPD-Based Maintenance (Airbus/Boeing Guidelines)
- FAA Approved CAMP (Continuous Airworthiness)
- MSG-3 Based Reliability Maintenance (Modern Airlines Use This)
- Hourly-Based Maintenance for Part 135 Charter Operators
Custom Maintenance Plan for A340-600 & B747-400
| Maintenance Type | Requirement | Frequency | Who Performs It? |
| Daily Check (Transit Check) | Visual walk-around, fluids check, systems check | Before every flight | Flight crew or mechanics |
| A-Checks (Line Maintenance) | Cabin, avionics, systems, oil checks | Every 600-800 flight hours (A340-600 & B747-400) | Line maintenance personnel |
| B-Checks (Optional, Some Airlines Skip It) | More detailed systems and engine checks | Every 3,000-4,000 flight hours | MRO/Line Maintenance |
| C-Checks (Heavy Maintenance Check) | Full aircraft inspection, structure checks, systems tests | Every 18-24 months or 6,000 flight hours | FAA/EASA Part 145 MRO |
| D-Checks (Structural Inspection & Overhaul) | Full aircraft teardown, corrosion prevention, landing gear overhaul | Every 6-12 years or 36,000 flight hours | Heavy Maintenance Facility (e.g., Lufthansa Technik, HAECO, SR Technics) |
| Engines & APU Overhaul | Based on manufacturer Time Between Overhaul (TBO) | Every 20,000+ flight hours or condition-based | OEM or FAA Repair Station |
| Landing Gear Overhaul | Deep structural inspection & part replacements | Every 10 years or 18,000 cycles | FAA-approved MRO |
Additional Requirements
✔ Structural Inspections:
- B747-400: Upper deck & forward cargo door stress inspections
- A340-600: Wing spar & fuselage section 19 stress monitoring
✔ Airworthiness Directives (ADs) & Service Bulletins (SBs):
- Mandatory compliance for FAA, EASA, Boeing, and Airbus directives
✔ Avionics & Systems:
- Transponder & Pitot-Static – Every 24 months
- RVSM (Reduced Vertical Separation Minimum) Check – Every 24 months
- ELT (Emergency Locator Transmitter) Inspection – Every 12 months
✔ Reliability Monitoring:
- Use MSG-3 methodology to optimize maintenance tasks and reduce downtime
Next Steps
- Determine Operational Model – Part 121 Airline vs. Part 135 Charter
- Select an FAA Part 145 Maintenance Provider – MRO (e.g., Lufthansa Technik, SR Technics, or local FAA/EASA-certified MRO)
- Set Up a CAMP Program – FAA/EASA-approved continuous maintenance plan
Yes, Part 135 charter operations can be stand-alone and do not need to be associated with a Part 121 airline. Many companies operate exclusively under Part 135 without having a Part 121 certificate.
Key Differences Between Part 135 and Part 121
| Regulation | Part 135 (Charter) | Part 121 (Airline) |
| Type of Operation | On-demand charter, commuter flights | Scheduled airline service |
| Aircraft Size | Smaller aircraft (≤9 pax typically) | Larger commercial aircraft |
| Operational Flexibility | More flexible, fewer regulations | Stricter regulations |
| Crew Requirements | Less stringent than Part 121 | Requires more training & crew experience |
| Maintenance Program | Can use Approved Aircraft Inspection Program (AAIP) or standard Part 91.409 inspections | Must have FAA-approved Continuous Airworthiness Maintenance Program (CAMP) |
Standalone Part 135 Charter – Key Requirements
✔ No airline association needed – Can operate as a private charter company
✔ FAA Part 135 Certificate – Required for on-demand or commuter flights
✔ Operational Control – Company must directly oversee flights, crew, and maintenance
✔ Maintenance Program – Must comply with FAA Part 91.409 or CAMP (if large aircraft used)
When Does Part 135 Need to Work With a Part 121 Airline?
🔹 If using large aircraft (>9 pax, e.g., A340-600, B747-400) – Must comply with stricter FAA rules
🔹 If transitioning to scheduled airline operations – Would require a Part 121 certificate
🔹 If wet-leasing aircraft from a Part 121 airline – Would need FAA approval
Step-by-Step Guide to Setting Up a Part 135 Charter Operation
Operating a Part 135 charter business requires FAA certification and strict compliance with regulations. Below is a detailed roadmap for obtaining a Part 135 Air Carrier Certificate.
Step 1: Business Planning & Compliance Preparation
Before applying for certification, you must define your operation and ensure regulatory compliance.
✔ Choose Your Business Model:
- On-demand charter (private flights)
- Commuter operations (scheduled small aircraft service)
✔ Select Aircraft Type:
- Small aircraft (≤9 passengers) → Less regulatory burden
- Large aircraft (>9 passengers, e.g., A340-600, B747-400) → Stricter FAA oversight
✔ Obtain Required Insurance:
- Minimum $300,000 per passenger liability insurance (for smaller aircraft)
- Higher coverage required for large aircraft
✔ Secure Operational Base & Maintenance Support:
- Must have approved maintenance facilities (FAA Part 145 Repair Station or in-house maintenance program)
✔ Develop a Financial Plan:
- The FAA will review financial capability to sustain operations
Step 2: FAA Part 135 Certification Process
The FAA’s Five-Phase Certification Process ensures compliance before granting the certificate.
1️ Pre-Application Phase
- Contact the FAA Flight Standards District Office (FSDO) to start the certification process
- Submit Letter of Intent (LOI) to operate under Part 135
- Meet with FAA inspectors to discuss operational structure, aircraft, and compliance
2️ Formal Application Phase
- Submit the following documents:
✔ General Operations Manual (GOM) – How your business will operate
✔ Training Program Manual – Pilot & maintenance staff training requirements
✔ Hazardous Materials (HAZMAT) Manual – If applicable
✔ Aircraft Maintenance Program (AAIP or CAMP)
✔ Aircraft Lease & Insurance Agreements
✔ Pilot & Crew Rosters – Showing qualified personnel
3️ Design Assessment Phase
- The FAA will review documents and manuals
- Conduct background checks on management personnel
- Evaluate financial stability
4️ Performance Evaluation Phase
- FAA inspectors conduct:
✔ Base inspection – Verify aircraft & operational facilities
✔ Pilot checkrides (135.293, 135.297, 135.299 checks)
✔ Maintenance system inspection – Ensure compliance with FAA Part 91.409 or CAMP
5️ Certification Phase
- If all inspections pass, FAA issues the Part 135 certificate
- You can now legally operate as a charter carrier
Step 3: Hiring Required Personnel
FAA mandates specific management positions for Part 135 operators.
| Position | Required for Small (≤9 Pax) Part 135? | Required for Large (>9 Pax) Part 135? | Qualifications |
| Director of Operations (DOO) | ✅ Yes | ✅ Yes | ATP-rated pilot, 3+ years experience |
| Chief Pilot | ✅ Yes | ✅ Yes | ATP-rated, experience on aircraft type |
| Director of Maintenance (DOM) | ✅ Yes | ✅ Yes | FAA A&P License, 3+ years experience |
| Chief Inspector | ❌ No | ✅ Yes | FAA IA Certification (for large aircraft) |
Pro Tip: If you operate large aircraft (e.g., A340-600, B747-400), you may need additional safety & compliance officers per FAA guidelines.
Step 4: Setting Up Maintenance & Safety Programs
FAA requires a robust maintenance program to ensure continued airworthiness.
✔ For Small Aircraft (≤9 Pax):
- Follow FAA Part 91.409 Inspections
- Can use an Approved Aircraft Inspection Program (AAIP)
✔ For Large Aircraft (>9 Pax, A340/B747):
- Must operate under a Continuous Airworthiness Maintenance Program (CAMP)
- Requires FAA-approved Part 145 Repair Stations for heavy maintenance
✔ Implement a Safety Management System (SMS):
- Required for large aircraft charter
- Recommended for all Part 135 operators
Step 5: Launch & Compliance Management
Once certified, you must maintain continuous FAA compliance:
✔ Conduct internal audits to ensure operational efficiency
✔ Track pilot & crew training compliance
✔ Monitor airworthiness directives (ADs) and service bulletins (SBs)
✔ Ensure flight logs & maintenance records are up to date
Summary: Timeline & Costs
| Stage | Time Estimate | Estimated Cost |
| Pre-Application | 1-2 months | Free |
| Formal Application | 3-6 months | $20,000+ (document prep, consultants) |
| FAA Review & Inspections | 3-6 months | $50,000+ (aircraft setup, insurance) |
| Final Certification | 1-2 months | Varies |
| Total Time to Certify | 6-12 months | $100,000+ (varies based on aircraft type) |
✅ FAA Part 135 manual templates
✅ Qualified personnel (DOM, DOO, Chief Pilot)
✅ Best maintenance program (AAIP vs. CAMP)?