Inspecting planes does require a lot of skill and knowledge. But one doesn't need deep expertise to detect loose bolts. My experience is that when quality brea

Inspecting planes does require a lot of skill and knowledge. But one doesn't need deep expertise to detect loose bolts. My experience is that when quality breaks down, the effects are visible at multiple scales and multiple places. Who knows what else is non-compliant in the 737 MAX assembly line (surely this is why the FAA announced an audit). Loose bolts happen because multiple layers of protection were bypassed. https://en.wikipedia.org/wiki/Swiss_cheese_model https://en.wikipedia.org/wiki/Swiss_cheese_model