Surely you’ve asked yourself why the routes followed by the aircraft, especially long distances, follow a curved route rather than a straight line. As we all know, and confirmed by Euclid, the shortest distance between two points is a straight line, right?
In that case, why do aeroplanes not fly in a straight line? Why does a flight from Madrid to Puerto Rico pass by Greenland? We will explain here.
The shortest route is not always a straight line
The geodesic lines are the lines which establish the shortest distance between two points of any surface, but it’s important to note, they are not always straight. In fact, it depends on the surface in question.
On a 2D map, the geodesic lines between any two points are straight. But on a curved map, how is the land surface? The geodesic lines are curved.
Also, as the Earth is not really a sphere as it’s slightly flattened by its poles, we find the geodesic lines are arches with higher or lower curvature, depending on the distance which separates two points and the latitude difference between them.
Source: Great Circle Mapper
So, how are aeroplane routes established?
In practise, it’s not that simple to calculate the shortest route for an aeroplane. There are a multitude of factors to consider, such as each country’s airspace restrictions, the weather, the location of the different airports on route, or the movement caused by the rotation of the Earth.