Why Flight Paths Look Curved on a Map

If you have watched a flight tracker draw an arc that bows north over Canada or Russia instead of running straight across the map, you have already asked the question this piece answers: why are flight paths curved when the straight line on the map looks so much shorter? The short version is that the map is the thing that is wrong, not the pilot. A straight line on most flat maps is not actually the shortest way between two points on a round planet, and the curved line you see traced on a tracker is usually the airline flying the genuinely shortest route available, called a great circle. This guide covers what a great circle actually is, why the flat map distorts it into a curve, how that plays out on two real long-haul routes, and where the curve gets the most dramatic.

What a great circle actually is

Earth is a sphere, near enough for this purpose, and the shortest path between any two points on a sphere is not a straight line in the everyday sense, because there are no straight lines on a curved surface. The equivalent of a straight line on a sphere is called a geodesic, and on a sphere every geodesic is part of a great circle: the line you get by slicing the sphere with a flat plane that passes through its exact center (Wikipedia, "Great-circle distance," captured 2026-09-23). The equator is one great circle. Any line of longitude paired with its opposite meridian on the far side of the globe forms another. Between any two ordinary points, there is exactly one great circle that connects them, and the shorter of its two possible arcs is the shortest distance between those points along the surface of the planet.

That is the whole idea behind a great-circle route: it is not a special or unusual path an airline chooses for effect, it is simply the geometrically shortest way to get from one airport to another without tunneling through the Earth. Flight planners compute it for exactly that reason, because a shorter route means less fuel burned and less time in the air, which matters on every long-haul sector an airline flies.

Why a straight line on the map is not the shortest line in the air

The confusion comes from a mapmaking problem that is centuries old. Most of the world maps people grew up with, including the ones behind a lot of flight-tracking apps, use some version of a projection that turns the curved surface of the globe into a flat rectangle so it can be printed or displayed on a screen. The most common of these, the Mercator projection, does that by wrapping the sphere in an imaginary cylinder and projecting the surface onto it (Wikipedia, "Mercator projection," captured 2026-09-23). It is a useful projection for a specific job: it preserves angles, so a compass bearing drawn as a straight line on a Mercator map is a real, constant bearing you could sail or fly by. But that same property forces the map to stretch distances further and further apart as you move away from the equator, which is why Greenland looks roughly the size of Africa on a Mercator map even though Africa is about fourteen times larger in reality.

A straight line drawn on a Mercator map is what is called a rhumb line: a path of constant compass heading. Except along the equator or a meridian, a rhumb line and a great circle are two different paths, and the rhumb line is longer, sometimes by a lot, once the two endpoints are far apart in longitude (Wikipedia, "Mercator projection," captured 2026-09-23). Flip that around and the answer to "why are flight paths curved" falls out on its own: the great circle route, the one that is actually shortest in the real world, is the one that gets drawn as a curve when you plot it onto a flat, distorted map. The curve is not the plane taking a detour. The curve is the map failing to represent a sphere honestly, and the straight line you expected to see would have been the longer path.

Seeing it on a real route

The effect is easiest to see on a route that runs a long way across the top of the globe rather than along the equator. Take Singapore to London. On a flat Mercator map, a straight line between the two would appear to run more or less due northwest across the Middle East and southeastern Europe. The great-circle route between Singapore and London instead climbs much further north than that straight line would suggest, and on many days it passes closer to Central Asia and Eastern Europe before descending into London, because that arcing path over the higher latitudes is the shorter one on an actual sphere. That is the shape you are looking at on a tracker's map view: a curve on the flat screen, and a straight, direct line if you could look at the same route on a globe.

The same logic holds on routes that run mostly east to west across an ocean rather than north to south. Newark to Santo Domingo is shorter and stays closer to the equator, so the curve is much gentler than it is on a route like Singapore to London, but the same great-circle geometry is doing the work either way. On a route that runs mostly along the equator, the great circle and a straight Mercator line nearly coincide, because distortion on a Mercator map is smallest near the equator and grows the further from it you travel. The curve you notice on a tracker's map is really a readout of how far from the equator, and how far in longitude, a given route travels.

Where the curve looks the most dramatic

The routes where this effect is most visible, and most often misread as the plane "going the wrong way," are the long east-west or diagonal routes at higher latitudes: city pairs across the North Atlantic, across the northern Pacific, or between Europe and East or Southeast Asia. A hub like Dubai sits at a latitude and a geographic crossroads that puts it on the great-circle path for a wide range of long-haul city pairs between Europe, Africa, South Asia and points further east, which is part of why it functions as a connecting hub for so many of them: the shortest path between two other cities often runs close to it anyway. If you are watching a route like that on a map and it bows noticeably away from the straight line you would have drawn with a ruler, that bow is the geometry working correctly, not a sign the flight is off course.

There is a genuine limit worth naming here too, since flight planners do not fly the pure great circle on every route regardless of anything else. Winds aloft, restricted airspace, air traffic routing structures and fuel-optimal cruise altitudes can all shift the actual flown path away from the theoretical shortest arc, sometimes by a meaningful distance. The great circle is the geometric floor, the shortest distance physically possible between two points on the globe. The route an aircraft actually flies on a given day is planned around that floor, adjusted for the real atmosphere and airspace it has to cross that day.

How TrackMyWings™ helps

TrackMyWings™ is a live flight-tracking platform in development, built for people who want to understand a specific flight rather than memorize aviation geometry. A private beta shipped on 2026-08-24, Android only, on the Play internal testing track with a small group of named testers. Public launch has no fixed date; it depends on trade-mark clearance and on the app being good enough to earn the download.

Questions people ask

Why do flight paths curve on a map instead of going straight? Because most flat maps distort distance the further you get from the equator. The curved line is usually the great circle, the actual shortest path between two points on a sphere; a straight line drawn on the map would represent a longer real-world distance.

What is a great circle route? The shortest path between two points on a sphere, found by slicing the sphere with a flat plane through its exact center and following the resulting circle. Every geodesic on a sphere is part of a great circle.

Is the curved line always the exact route a plane flies? Not always exactly. It is the geometric shortest path, but wind, restricted airspace and air traffic routing can shift the actual flown track away from the pure great circle on a given day.

Why does the curve look bigger on some routes than others? Distortion on a common flat map is smallest near the equator and grows toward the poles, so a route that runs mostly east-west near the equator curves gently, while a route that reaches into high latitudes, like many routes between Asia and Europe, curves much more dramatically.

Does this affect short domestic flights the same way? Barely. Over short distances the difference between a great circle and a straight line on most maps is small enough to ignore. The effect only becomes visually obvious once a route spans a large distance in longitude, latitude, or both.

Sources

• Wikipedia, "Great-circle distance," https://en.wikipedia.org/wiki/Great-circle_distance, captured 2026-09-23
• Wikipedia, "Mercator projection," https://en.wikipedia.org/wiki/Mercator_projection, captured 2026-09-23