Regardless of what you think of rich ass corporations, this is an important liability issue. United shouldn't be on the hook for losing money when it was Boeing's fault
There ought to be an outright ban on Boeing airplanes and a class action lawsuit against the company for putting peoples' lives in danger and causing reputation damages to flight companies.
Alaskan Airlines as well. They kept getting pressure cabin alerts, never finding the problem, and just resetting the warning system. They even went so far as to instruct that this plane was not to go over water so it could land if it had an issue.
The door plug is absolutely on Boeing but AA was negligent on how it handled the warning it got multiple times before the blowout happened.
Boeing wrote the service manuals and maintainance schedule. If the airline was supposed to do a test to catch the mistake but didn't, boeing would mention it.
A door plug is part of the fuselage, and it is hidden behind wall panels. An airline isn't expected to disassemble the entire interior to check the structure upon taking delivery of the plane.
The pressure fault the plane had before the blowout wouldn't have lead to a check of the door plug even if it had gotten the service before the blowout.
There are like a million bolts on a plane, and not all are easily accessed or listed as things to check on regular maintenance. It sounds like these were not easily accessible.or seen and not something that would be regularly checked.
Like how a lot of bolts on cars and trains and aubways are not readily accessible or checked before the vehicle is put into seevice becsuse it is assumed that the factory's quality control took care of them.