As stated in the video, if the world were round, a pilot would having to be dipping the nose of the plane down every five minutes to stay around the curve of the world. In a plane there is an artificial horizon based on the gyroscope and if you spin the gyroscope, it will want to stay upright. Although, if the plane has a gyroscope and it starts flowing the curve of the earth, it will stay upright which means the artificial horizon would start to roll backwards but, it does not so therefore, the plane flies over a flat