Mechanical interruption summary report

This regulation requires Part 121 air carriers to submit a monthly summary report to the FAA by the 10th day of each month covering the previous month's operations. The report must include three categories of events:

Mechanical interruptions — Any flight interruption, unscheduled aircraft swap, or unplanned stop/diversion caused by mechanical issues that don't rise to the level requiring immediate reporting under § 121.703 (which covers more serious mechanical failures).

Engine removals — Engines taken out of service early due to problems, broken down by engine make/model and aircraft type.

Propeller featherings — In-flight propeller featherings (except those done for training or demonstration purposes), listed by propeller type, engine, and aircraft.

This reporting helps the FAA track reliability trends and identify potential safety issues across the carrier's fleet before they become serious problems.

*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.*