FENZO, A bit of "apples and oranges" here with a comparison to airline structural maintenance. Not quite sure that is a valid comparison.
1) "General public" lives are at risk in an airliner, and they have faith that the government (FAA) and aircraft manufacturers (Boeing, Airbus, Embrier, etc) have tested and approved repair methods to fix primary load carrying structures which if they fail would lead to loss of the aircraft. Often engineers design redundant load paths into primary structures for just such occurances (just like the airlines require two pilots in the front).
2) Structural failures in aircraft have the potential to kill a number of people who have no knowledge of a botched structural failure. If you have your FGT frame fixed and the repair fails leading to a deadly accident, two people may be killed and you knew a frame structural repair was made to your car.
3) Aircraft company engineers perform extensive analysis and testing of recommended primary structure repairs. It is simply too costly and impractical to tell the airline company just throw the aircraft away without fixing it. From a liability perspective it is certainly fine to tell the product owner to just discard the product and purchase a new undamaged one (as is Ford's position on frame repairs). But for high cost items worthy of an investment of technical review and repair testing, generally a fix can be made.
Perhaps a stretch, but having been both an aircraft mechanic and engineer responsible for aircraft modifications (military) I can tell you in general your points concerning repair are theoretically accurate but not necessarily in practice. Each repair is not extensively analyzed, period. In fact, our tongue in cheek assessment about many an aircraft repair was "Cut to form, hammer to fit, paint to match". Don't get me wrong.... I think that is OK.
A well intentioned teenager in China is likely performing significant repairs on the jets we ride, and they don't fall out of the sky. A well intentioned frame repair on a car is apples to apples IMO.
The evaluation of damage repaired valuable vehicles would be more useful if it were akin to aircraft. A salvage car title tells you nothing other than the repair estimate was too costly vs the value of the car and forever hangs a stigma on the vehicle. As you mentioned that is more impractical with aircraft so they end up being repaired but airworthy, and no less valuable. A car could be just as easily repaired but roadworthy, and no less valuable (like the GT40s Ralphie mentioned).
Just a thought exercise, I'm not trying to convince anyone of anything. It is interesting/confusing that philosophies span the spectrum. :thumbsup
A two second search resulted in a bunch of interesting info, for example:
http://investigativereportingworksh...heaper/story/outsourcing-airline-maintenance/