Miscalculation Or Wishful Thinking?

The BBC reported today, in part, the following quoted below. - ref.  http://www.bbc.com/news/world-us-canada-43818752

"What have investigators said?

NTSB chairman Robert Sumwalt told reporters that a fan blade had broken off due to metal fatigue and that a second fracture had been recorded about halfway along its length.
He could not say if the incident indicated a fleet-wide issue with the Boeing 737-700.

Mr Sumwalt also said a casing on the engine was meant to contain any parts that come loose but, due to the speed, the metal was able to penetrate the shell.
The FAA did not say how many engines would be inspected. It said that any fan blades that failed the inspection would have to be replaced.
In 2016, a Southwest Airlines flight made a safe emergency landing in Florida after a fan blade separated from a similar CFM engine.
Debris ripped a hole more than a foot long in the fuselage of the jet above the left wing, causing cabin decompression. An investigation into that incident also found signs of metal fatigue, according to the NTSB."  There were other fan blade failures in recorded history.

There is no doubt, in my mind, that economics won the day, when it came to taking proper corrective action, following a similar Fan Blade failure in 2016 on a similar engine, experienced by the same Airline (Southwest).  The failure rate, and the Mean-Time-Between Failures (MTBF) are certainly (or should be) known, based on Lab testing and limited field data, and depending on the 'Confidence Level', at which these were calculated, timely re-inspection of in-service fan blades should ensure that such catastrophic failures are not part of the consumer's flying experience.

Apart from inspecting for evidence of cracks the Airlines must also ensure that the fan blades were properly shot-peened, when required.   This process, when properly performed, will prevent cracks in critical parts.  For info on this process follow this link.  https://www.youtube.com/watch?v=l05Bqotp4N0

The irony in all this is that when some years ago, some fellow had explosives in his shoes, everybody was required, and still is, to have their shoes screened 100% of the time, but when a critical part, such as the fan blade of a jet engine explodes in-flight, we do not take similar drastic actions, it appears.  Therefore, I say, apparently, the industry is only interested in preventing the loss of life, when the inconvenience affects only the consumer, and no tangible costs are involved for the corrective action.