>it can be shown that at the aircraft level the safety is somewhere between 10 7 to 10 8 so now the aircraft potential for catastrophic failure is well below what 1309 requires yet the FAA does nothing about it. <
Of course! Actually air travel is no better than about E-6 for all causes including the pilots, so why dump on the aircraft design that only makes up 10%
The FAA is just being practical in regulating what can be regulated (system safety under 1309). It wouldn't be very practical to require boolean calculations on fuel tank explosions where one doesn't forsee an ignition probability or on a rudder tearing off under overstress.
On the other hand this thread drift kind of supports the lack of statistical evidence that KAL is a lousy airline, but the piloting stories persist in spite.