I recently did a public tour of one of Airbus' major assembly lines. I remember the tour guide telling us, that their customers (the airlines) either have their own QA people on the line when their planes get assembled, or pay another company to do it for them.
I would like to phrase this as “trust and verify”, because the state of trust arises from being open to verifiability, contrary to common misconception that they are against each other.
They are naturally against each other, which is why the "but" statement is meaningful.
"Slow and steady" vs "fast but steady".
"Move fast and break things" vs "move fast but don't break things".
Plus the fact that these machines have a 30 year working life.