While investigators are busy trying to figure out what may have caused the crashes of Boeing’s 737 MAX jetliners, a whistleblower who was formerly East Asia Supply Chain Manager of Boeing’s flight control system contractor has intensified his efforts to bring to light an issue that has been troubling him for the past three years: substandard parts made in China with non-aerospace material have been installed in Boeing 777 and 737 planes that are still in service.