"Boeing has yet to satisfy the FAA that it has fully understood and corrected what went wrong that day." This appears to be the heart of the problem, how come

"Boeing has yet to satisfy the FAA that it has fully understood and corrected what went wrong that day." This appears to be the heart of the problem, how come it's the FAA holding you up on this and not your own engineering department? A solid foundation in design and engineering would require that if an event like this happened you'd rip down the whole structure until you got to the problem, from where you could confidently move forward knowing you know your systems.