The rapid retrofit schedule, which was put in place after durability issues were uncovered on a ground-test engine in June, will enable Boeing to stay on track toward a likely first-flight attempt in January.

“It’s a good news/bad news thing,” revealing the first details of the unexpectedly extensive retrofit package. “The bad news is we found a problem in the engine; the good news is we fixed it, and the biggest impact has been on the schedule.

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