Other airlines also voiced objections.
The deceased passenger, identified as Albuquerque bank executive Jennifer Riordan, died after being partially sucked out the window.
But he advised it was too soon to question the safety of the engines or the Boeing 737s.
In 2016, U.S. officials also blamed metal fatigue on a similar engine failure on another Southwest Airlines plane in Florida. "Sometimes the contract of carriage does not answer the particular questions". CFM commented that the longer deadline be shortened to 12 months.
"When the parts are off the aircraft and in the repair station a more thorough level of investigation can be performed that would be impractical whilst the engine is on the aircraft wing".
Southwest did not respond to inquiries for further information.
The FAA never issued a final decision.
The FAA said it will issue a safety directive for ultrasound inspections of CFM56 engine fan blades that have accumulated a specified number of flight hours. But they do know that two successive, unlikely events contributed to it.
The CFM56 engine on Southwest flight 1380 blew apart over Pennsylvania on Tuesday. "Yes", said Tony Kern, CEO of Convergent Performance, which consults on risk management for companies, including airlines.
U.S. National Transportation Safety Board (NTSB) investigators responding to the Philadelphia airport immediately focused on a missing fan blade in the damaged engine. As of Dec. 31, 2017, the carrier reported operating 693 737-700/800s.
Emergency alarms on the plane acted properly and the plane rolled at a severe 41-degree angle after the left engine failed, he said. CFM engines are produced by CFM International, a joint venture between General Electric and France-based manufacturer, Safran. Critics said the airlines were slow to act.
Experts said it's not unusual for such cracks to be located in spots that aren't easy to see. The flight was heading from LaGuardia Airport in New York City to Dallas' Love Field.
Laurie outlined that it is advisable to keep your seatbelt on while seated, in case something like turbulence occurs. The letter concludes with, "Again, please accept our heartfelt apologies". Each CFM56 engine has 24 blades.
Tuesday's emergency broke a string of eight straight years without a fatal accident involving a US airliner.
Former flight attendant Bobby Laurie shared the photo with a caption reminding travellers to use the mask properly.
Capt Shults, a New Mexico native, graduated with university degrees in biology and agribusiness before joining the military.
Plane crashes are exceptionally rare. The impact, whiplash, and destruction at the front of the plane could have seriously injured or killed passengers seated in that area - likely those in the first class and more desirable seats.