Sadly one passenger was killed and others injured when the engine on the
Southwest 737 failed today.

The turbine blades in jet engines are under stress and heat during
operation and are the usual failure mode in cases like this.
There is a "containment ring" that is supposed to prevent the flying
turbine blades from damaging the aircraft but it appears that it didn't
capture all the flying parts today.

Heard the head of the NTSA state that this failure happens "3 or 4 times
a year".

It isn't confirmed yet that turbine blade failure is the cause of this
particular event but it most likely is.

We built a system for Pratt and Whitney back in the 80's to deposit
thin film strain gauges and thermocouples (temp measurement) on the
turbine blades for real time operating monitoring of the turbines.