I would strongly suggest that Nick redo the math. The FAA design guidelines stipulate that you can not have a failure of a mechanical or electronic component as well as structural elements that can bring down an aircraft no more frequently than one time in a billion hours of operation. They do not reference emplanements or seat miles they reference hours of operation for the fleet. That includes all aircraft of the same type operated by any number of operators.
How many emplanements were there on the 737 models several of which crashed due to a faulty tail power control unit or a damper? How many hours did these aircraft accumulate? I can guarantee that it was well below the 1 billion mark no matter how many people boarded the aircraft type.
How many emplanements were there on the 767 series at the time of the Lauda Air crash? How many hours had been accumulated at the time of the crash? Again well below 1 billion hours.
How many emplanements were there on the 737 series when an engine exploded at the Manchester Airport in the UK? How many hours had accumulated on the 737 series? Again the answer is the same.
I could go on and on but it would always be the same. The commercial aircraft have never met the design goals set up by the FAA and they never will. If there is a crash and the NTSB finds the reason the FAA will perform a cost benefit analysis. They apply a cost of human life of approximately 2.5 million dollars. In the analysis if it is proven that the cost of making the repair fleetwide is in excess of the number of persons killed times 2.5 million dollars in another crash of that aircraft type they will not require the change. This is definitely in favor of the airlines.
Another point, any reference I have made in my post above relative to safety or failure came from the FARs and Advisory Circular 1309 and Advisory Circular 23.1309-1C, which are published by the FAA and not the NTSB.
I think we have deviated from the reason for this thread.