Supplemental inspections

This regulation requires airlines operating larger transport aircraft under Part 121 to implement enhanced inspection programs focused on "fatigue critical structure"—parts of the airplane where fatigue cracks could lead to catastrophic failure.

It applies to turbine-powered transport aircraft certified after January 1, 1958, with either 30+ passenger seats or 7,500+ pounds payload capacity. Alaska intrastate operations are exempt.

Since December 2010, airlines must have FAA-approved damage-tolerance inspections in their maintenance programs that specifically target fatigue-prone structures. The program must also address how repairs, alterations, and modifications might affect these critical areas or interfere with required inspections.

All changes to the maintenance program related to these requirements need approval from both the responsible Aircraft Certification Service office (for the repair/alteration procedures) and the airline's Principal Maintenance Inspector (for program changes). This ensures aging aircraft structures receive systematic monitoring to prevent catastrophic structural failures.

*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.*