Comment by ghaff

The thing is that you end up having to be very process heavy. From an efficiency, rather than safety perspective, I had an offer from (and interviewed with--in that order) Boeing many moons ago. The thing I remember from a long-ago dinner after that interview was a guy who had spent a couple of years on some design tweak that saved some fraction of a percent on fuel consumption. That's the sort of thing that most engineers do in aviation (where it's perfectly appropriate).