I referenced this without the detail in an earlier post. Nicely done! The shortest distance between two points on Earth is a great circle route. This is easily illustrated with a string between two distant points on a globe (yes, a globe). If you pulled up a computerized flight plan with absolutely no enroute wind, you would still see both course and heading constantly changing. That said, it’s still a long ride back from Beijing. I still have certain content ignored, so God only knows what was posted to prompt your response.