Originally Posted by
RUTUS
I read somewhere that Spirit installs the plugs in a provisional manner but that they are then removed by Boeing because they need access when they complete the aircraft. It seems very likely that Boeing would at least open them as normally there is a door there and their procedures would be based on that.
If the bolts are missing or incorrectly installed Boeing would be responsible.
I haven't been able to verify the information but those interested in the blame game probably should try before absolving Boeing.
FYI I tried to answer this in genetic terms in post
www.pprune.org/accidents-close-calls/656760-alaska-airlines-737-900-max-loses-door-flight-out-pdx-19.html#post11571259