Why airplanes fly in an arc on cross country or transworld flights.?
The line appears as an arc only because you are looking at the path on a two dimensional flat surface instead of the three dimensional curve of the Earth. The equator and all lines of longitude are called “great circles.” The shortest distance between two points on the surface of a sphere is the great circle route. Connect the points with each other and the center of the Earth. If you sliced through the Earth through these three points, the edge of each hemisphere would be a great circle. Draw a great circle that connect the two points on the surface of the globe. When looked at from directly overhead, the path is appears straight, but look at it from any other angle and the line appears curved, Since the arc is a portion of a circle, it is ALWAYS a curve, it just appears straight when looked at from exactly one place, directly overhead. These are used for air travel routes because it is the shortest distance between two points which means the least amount of time and gas, simple. This
