The parts that are the same can easily be a problem. Take, for instance, the emergency exits (this was about getting the NG certified in Japan almost 25 years

The parts that are the same can easily be a problem. Take, for instance, the emergency exits (this was about getting the NG certified in Japan almost 25 years ago BTW): https://www.flightglobal.com/news/articles/boeing-wins-first-round-of-jaa-certification-row-over-new-21773/ https://www.flightglobal.com/news/articles/boeing-wins-first...