Why problems at a key Boeing supplier may help explain the company's 737 Max 9 mess

A 737 Max 8 undergoes final assembly inside Boeing's factory in Renton, Wash., on March 27, 2019. Kansas-based Spirit AeroSystems makes the fuselages and ships them to Washington. A series of production issues at Spirit have led to problems. (Ted S. Warren/AP)

At the factory in Wichita, Kan., where Spirit AeroSystems builds the fuselage for the Boeing 737 Max, management would sometimes throw a pizza party to celebrate a drop in the number of problems reported on the line.

But Joshua Dean says many of the workers knew something was off.