In 2018, after a fractured fan blade led to the failure of a CFM56-7B engine on a Southwest Airlines 737, resulting in the death of a passenger, the U.S. Federal Aviation Administration directed a one-time ultrasonic inspection of all 24 fan blades on engines with more than 30,000 flight cycles.

A similar incident two years prior prompted the engine’s manufacturer, CFM International, to recom-mend inspections of fan blades on CFM56-7B engines (Fig. 1) with 20,000 cycles. All told, the FAA and CFM bulletins covered approximately 3,160 engines, or 76,320 separate fan blades.