I used to work for a company that was Spirit's largest supplier. Spirit contracts a bunch of parts out to smaller manufacturing companies. We would manufacture parts, process them (paint and anodizing), then assemble them at all of our facilities, then they would get shipped to Wichita for further assembly by Spirit. The 737 MAX has been Boeing's fastest selling plane in recent history, so you can imagine the pressure on the manufacturing contractors to get their parts out the door. After seeing everything from the inside, I personally wouldn't fly on a 737 MAX. I would stick with Boeing's older models or choose an airline that has primarily an Airbus fleet.