Airframe Hours & Cycles
How much life the airframe has used. Hours measure time in service; a cycle is one takeoff and landing, and it is cycles that drive fatigue.
Pressurising and depressurising the fuselage on every flight is what fatigues the structure, so inspection thresholds for cracking are set in cycles. A short-haul aircraft accumulates cycles far faster than hours relative to a long-haul one of the same age.
Case files carry both figures where they are known, together with the last major check, because they are the frame of reference for any maintenance or structural finding.
Related terms
The airframe itself broke, usually through fatigue cracking, corrosion, an improper repair, or loads beyond what the structure could take.
An engineering or maintenance action (a part fitted wrongly, an inspection missed, a repair done off-manual) contributed to the accident.
A legally binding instruction from a regulator requiring an inspection, repair or modification on a type. Unlike a recommendation, compliance is mandatory.