> The relatively good news for Boeing is that because the test failed so explosively at just 1% shy of meeting federal requirements, it will almost certainly not have to do a retest. Regulators will likely allow it to prove by analysis that it’s enough to reinforce the fuselage in the localized area where it failed.

I don't understand this. So they did a test, and it failed at 99%. They reinforce that one area where it failed, and show by analysis that the reinforced area would have made it to at least 100%.

OK, but what about the rest of the fuselage? The rest was only tested to 99%. Couldn't there be another place that fails at, say, 99.5%, which wasn't detected in the first test because the place that fails at 99% stopped the test?

Edit: I would guess that during this kind of test they have the plane heavily instrumented with things like strain gauges so they can understand how it reacts and see if it is behaving according to spec. So maybe it is the case that the data from the rest of the fuselage showed that it would have made it to 100% if the test had continued, and only the area that failed was in trouble. That could explain why they aren't require to do another test.

That still leaves me unsatisfied, though. Presumably analysis of the design before the test said it would make it to 100%. If the failure was not due to a manufacturing defect in that particular fuselage, then it suggests that they analysis was not adequate. But then what assurance is there that their analysis that shows that the reinforcement would hold is good?