My god! I can't believe this! The plane goes straight and does not need to steer if you maintain altitude to the ground. Like clouds do. Clouds do not drift off to space according to basic physics and earth science. 30,000 feet above China then 30,000 feet above America then 30,000 feet above Europe, then 30,000 feet above China then 30,000 feet above America, without turning the plane, only paying attention to altitude will do a complete circle. This proves the Earth is round. If it were flat, you would need to steer the plane or you would go off of the world. If you still can't understand this, then there is no other way to explain it to you.