Turbofan engineer anon again.
Fan blade failure due to low cycle fatigue. LCF is tightly managed due to catastrophic consequences. Unusual failures, outside of predicted LCF life-limits, do occur. It sucks to have to react to it.
https:// www.ntsb.gov/news/press-releases/Pages/PR20160912.aspx
I mentioned in an earlier bread that the FAA had proposed a new rule, directing ultrasonic inspection at next engine shop visit. These engines are incredibly reliable and stay on wing a long time. I doubt this engine has had the shop visit.
https:// www.federalregister.gov/documents/2017/08/25/2017-17828/airworthiness-directives-cfm-international-sa-turbofan-engines