Why is the American registration number n688cz of China Southern Airlines 777?

20 14 On February 25th, Boeing delivered a 777-300ER aircraft to China Southern Airlines, which was the first of the 10 777-300ER aircraft ordered by China Southern Airlines.

Such a big plane can't be transported from the United States to China by car, train or ship. The easiest way is to fly directly. Just as a car needs a temporary license to get on the road, so does an airplane. To go to heaven, you have to go through the supervision of more than N departments, and you need to register in the United States and give a "temporary license" before you can take off. So there is the "American registration number".