Maintenance, preventive maintenance, and alteration programs

This regulation requires Part 135 operators (commuter and on-demand air carriers) to establish and maintain formal programs for all maintenance work on their aircraft. The operator must ensure three key things:

First, all maintenance work—whether done by the operator's own mechanics or contracted out—must follow the procedures in the operator's FAA-approved maintenance manual. You can't just have outside shops do whatever they think is right.

Second, the operator must provide (or arrange for) qualified personnel, proper facilities, and appropriate equipment to do the work correctly.

Third, before any aircraft returns to service, it must be airworthy and maintained according to Part 135 standards.

In practice, this means Part 135 operators need documented maintenance programs that meet higher standards than Part 91 operations. The operator remains responsible for maintenance quality even when using outside repair stations, and must verify airworthiness before each aircraft flies passengers or cargo.

*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.*