Additional airworthiness requirements

This regulation sets additional airworthiness standards for aircraft operating under Part 135 beyond basic certification requirements.

Large airplanes (except commuter category) must meet the same enhanced airworthiness standards required for Part 121 airline operations, covering areas like equipment, systems, and performance.

Small airplanes with 10+ passenger seats must be certificated in either the transport or commuter category, or meet special additional standards if certificated in the normal category. This ensures aircraft carrying more passengers have safety features beyond what basic normal category certification requires.

The regulation also limits increasing passenger seating beyond what was used before August 1977 unless the aircraft meets transport category or specific enhanced standards.

Finally, it requires fire-resistant liner materials in large cargo compartments of transport category airplanes to contain potential fires and protect the aircraft structure.

These requirements ensure Part 135 aircraft carrying passengers have appropriate safety margins for commercial operations.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*