Shortcut: Why the Shortest Flight Path Is Not a Straight Line
Shortcut draws three routes between two airports and asks which one is shortest. It teaches one of geography's best surprises: on a flat map the shortest route is usually a curve.
A sphere, not a sheet of paper
The Earth is nearly a sphere. The shortest path between two points on a sphere is part of a great circle, a circle whose centre is the centre of the Earth. When you flatten the globe to make a map, great circles turn into curves.
Why flights curve towards the poles
Lines of longitude get closer together as you move away from the Equator. A path that bends towards a pole crosses fewer degrees of longitude per kilometre, so it is shorter. That is why London to New York, for example, passes well north of a straight line on a flat map.
The three kinds of route in the game
- The great circle is always the shortest.
- The straight line on the flat map is longer. This is the trap on Medium.
- Routes via another airport add a detour. The size of the detour depends on how far the hub is from the direct path.
Rules of thumb
- The further the two airports are from each other, the more the great circle curves.
- East-west routes in the same hemisphere curve towards the nearest pole.
- North-south routes are nearly straight, because they follow lines of longitude.
- On Hard the routes are within a few percent of each other. Pick the one that bends more smoothly towards the pole.
After you answer
Each route shows its length in kilometres, so you see exactly how much a detour or straight line costs.
Frequently asked questions
What is a rhumb line?
A rhumb line keeps a constant compass bearing. It is easy to navigate by but longer than a great circle on long routes.
Do pilots fly great circles?
Roughly, yes, adjusted for winds, airspace and safety. The great circle is the baseline.
Keep learning
Related guides: Overflown, Longer Flight, Route Ranking. Or browse all game guides, the geography games and the country pages.