[Retric]

You can definitely treat it as a design flaw and fix it without impacting most systems.

Designers need to make radical changes before cockpit windows would need to be updated. That specific example may not seem like much but there’s a lot of safety critical engineering that goes into such things and yet design flaws where still uncovered.

[breadwinner]

Sure you can bring over the "good parts" of the old plane, but if this design flaw is fixed then it is essentially a new plane. They will no longer be able to pretend it is the same as the old 737s (and that's what got them into trouble).

[Retric]

When you say “parts” it’s really complex systems. The 737 family of aircraft has gone through many revisions over 50+ years at this point.

The original 737-100 was 61,994 lbs empty and the 737-900ER was more than 50% heavier at 98,495 before they started calling them MAX. The 900ER was in many ways a radically different aircraft but got there through a long list of incremental changes leveraging the past.

That’s not to say new designs can’t be quite safe. The much newer A320 family are some of the safest aircraft flying with only 38 hull losses and 1505 fatalities, but do not mistake good design for inevitability.