99.99966% free of defects
I have no idea to what this applies
certainly not to individual parts like screws, pistons, solonoids, switches and jeezuz bolts.
Maybe with a good quality control program and sampling you might get 75%, but an awful lot of stuff on planes rarely gets the sampling to even validate the quality control.
The idea to achieve safety is to provide backup, like redundancy, alternate paths and trained pilots. That way it takes a lot of things going wrong to result in a catastrophic outcome (death and destruction)
again my belief is opposite a lawyer's
"if not for"
and instead I would still insist on
"
in spite of"
as the way to achieve safety in a complex machine of multiple systems called an airplane etc.