20 May 2026
Why do flight paths curve on maps? Learn about great circle routes, the shortest distance on a sphere, and how map projections distort aviation geography.
Look at any map showing long-haul flight paths and you'll notice something counterintuitive: the routes curve. They don't follow straight lines between departure and arrival cities. Instead, they arc dramatically across the map, sometimes passing over regions that seem completely out of the way. A flight from Sydney to London appears to swing far north through Asia. A flight from Los Angeles to Dubai tracks across the Arctic rather than following what looks like a more direct path across the Atlantic and Europe.
This isn't airlines being inefficient or pilots taking scenic routes for fun. These curved paths are actually the shortest possible distance between two points on Earth's surface. They're called great circle routes, and understanding why they work reveals something fascinating about how we perceive distance and direction on a spherical planet that we usually view on flat maps.
The disconnect between what looks direct on a map and what is actually direct in physical reality trips up even experienced travelers when they see their flight paths visualized. This guide explains what great circle routes are, why they matter for aviation, how they appear on different map projections, and what this means for understanding your personal travel patterns when you log flights in a platform like Jetmap.
Start with the definition: a great circle is the largest circle that can be drawn on a sphere. It's a circle whose center coincides with the center of the sphere itself, meaning it divides the sphere into two equal hemispheres. On Earth, the equator is a great circle. Every line of longitude paired with its opposite (forming a complete circle around the Earth) is a great circle. But most importantly for aviation, the shortest path between any two points on Earth's surface follows an arc of a great circle.
This might sound abstract, so here's a practical way to visualize it. Take a globe and two pieces of string. Pick two cities far apart—say Sydney and London. Try to connect them with a string pulled tight along the globe's surface. The string will naturally form a curve, arcing up and over regions between the two cities. That curved path is a great circle route. Now try to lay string along what looks like a straight line on a flat map between the same cities. On the globe, that string won't lie flat; it'll have slack and won't represent the shortest path at all.
The fundamental insight is that Earth is spherical (more precisely, an oblate spheroid, but close enough for this discussion). On a sphere, straight lines as we think of them don't exist except in three-dimensional space passing through the sphere's interior, which obviously doesn't help aircraft trying to fly along the surface. Instead, the straightest possible path along the surface follows a great circle arc.
Commercial aircraft follow great circle routes (or close approximations) for a simple reason: fuel efficiency. The shortest distance between two airports means less time in the air, less fuel burned, lower costs for the airline, and faster arrival for passengers. On short flights, the difference between a great circle route and what might look direct on a map is negligible. But on long-haul international flights, the savings become substantial.
Consider a flight from New York to Hong Kong. A naive approach looking at a flat map might suggest flying southwest across the United States, over the Pacific, past Hawaii, and eventually reaching Hong Kong. But the great circle route goes northeast over Canada, across the Arctic, past Russia, and down into Hong Kong. This northern route is several hundred kilometers shorter despite looking longer on many map projections. That distance savings translates to significant fuel savings and reduced flight time.
The effect is most dramatic on flights that cross large distances at high latitudes. A flight from London to Tokyo takes what seems like an incredibly northern path, tracking over Scandinavia, Russia, and Siberia. That's not bad navigation or complicated airspace restrictions. It's simply the shortest way to get there on a sphere. The curvature of the Earth means that paths at higher latitudes cover less longitudinal distance per kilometer traveled, making northern routes between European and East Asian cities shorter than they appear.
Of course, aircraft don't follow perfect great circle routes in practice. They deviate for several reasons: avoiding restricted airspace or conflict zones, following established air traffic control routes and airways, adjusting for weather (particularly strong headwinds or favorable tailwinds at altitude), avoiding regions with inadequate diversion airports for emergency landings (critical for twin-engine aircraft on extended oceanic flights), and maintaining safe distance from tall terrain or volcanic activity zones.
But these deviations are typically minor adjustments to a basic great circle path. The fundamental route structure follows the great circle principle because that's where the physics of distance on a sphere point aircraft.
Here's where things get visually confusing. We live on a sphere, but we view maps on flat surfaces: paper, screens, walls. Converting a three-dimensional spherical surface to a two-dimensional flat map requires a projection, and every projection distorts something. You literally cannot perfectly represent a sphere on a flat plane without distortion. Different projections choose different trade-offs in what they preserve and what they distort.
The Mercator projection is probably what most people picture when they think of a world map. It's the rectangular map where Greenland looks enormous and Antarctica stretches across the entire bottom. Mercator preserves shapes and angles (making it historically useful for navigation), but it severely distorts areas and distances, especially at high latitudes. On a Mercator map, great circle routes appear as curves, with the curvature most pronounced on long east-west routes and routes crossing high latitudes.
This is why your flight from Los Angeles to Tokyo looks like it's taking a huge detour north. On the Mercator projection, the curved path arcing up toward Alaska looks longer than a straight line across the Pacific would be. But on a globe or on projections that better preserve distance, you can see that the curved path is actually shorter.
Azimuthal equidistant projections center on a specific point and show accurate distances from that center point to anywhere else on Earth. These are useful for understanding flight routes from a particular hub airport. An azimuthal map centered on Sydney shows accurate distances and directions from Sydney to everywhere else. Great circle routes from Sydney appear as straight lines radiating out from the center. But routes that don't involve Sydney still appear distorted.
Gnomonic projections have a unique property: every great circle appears as a straight line. This makes them extremely useful for plotting flight paths because you can see the true shortest route between any two points simply as a straight line on the map. However, gnomonic projections distort distances and areas severely, and you can only show less than a full hemisphere at once. They're excellent for navigation planning but don't give an intuitive sense of geography.
Globe projections (which Jetmap offers as one viewing option) show routes as they actually exist in three-dimensional space. A great circle route on a globe view appears as a gentle curve along the sphere's surface—the natural path an aircraft would follow. This is the most accurate representation, but it's harder to see the full picture of all your flights at once compared to a flat projection.
The key takeaway is that when you log flights in Jetmap or any platform that visualizes routes, the apparent curvature of the paths depends entirely on which map projection you're viewing. The physical route the aircraft flew doesn't change. What changes is how that three-dimensional path on a sphere is represented on your two-dimensional screen.
The visual effect of great circle routing varies dramatically depending on where you're flying:
North-South routes (like Sydney to Singapore, or Los Angeles to Santiago) appear relatively straight on most map projections because they don't cross dramatically different latitudes. The great circle path and the apparent straight line are similar enough that the curvature isn't visually striking.
East-West routes at mid-to-high latitudes (like New York to London, or Tokyo to Los Angeles) show pronounced curvature on Mercator projections. These routes arc north of the direct line between cities because traveling at higher latitudes covers longitudinal distance more efficiently on a sphere.
Transpacific routes (like Sydney to Los Angeles, or Tokyo to Los Angeles) demonstrate dramatic curvature on standard maps. The great circle path swings well north, sometimes passing close to Alaska or the Aleutian Islands, rather than taking what looks like a straight shot across the central Pacific. In reality, those central Pacific islands are much further from the optimal path than they appear on Mercator maps.
Polar routes (like New York to Hong Kong, or London to Singapore) can actually pass over or very near the North or South Pole when the departure and arrival cities are positioned appropriately. These routes look bizarre on standard maps—arcing dramatically toward the poles—but make perfect sense on a globe.
Short-haul regional flights within relatively small geographic areas don't show much curvature at all. A flight from Sydney to Melbourne follows a path that looks pretty much straight on any projection because the distance is short enough that the curvature of the Earth between the two cities doesn't create a visually dramatic great circle effect.
When you log flights in Jetmap, the platform calculates the great circle distance between your departure and arrival airports and displays the route as a great circle arc on the map. This gives you an accurate visualization of the approximate path the aircraft followed (remembering that actual flights deviate slightly for the practical reasons mentioned earlier, but the great circle is the fundamental route structure).
You can view your flights on multiple map projections in Jetmap to see how the same routes look different depending on the projection:
Mercator view shows the traditional web map style. Your great circle routes will appear curved, with more pronounced curvature on longer flights and flights crossing higher latitudes. This projection is familiar and makes it easy to see where routes go in terms of conventional geography, but remember that the distances and areas are distorted, especially near the poles.
Globe view displays your flights on a three-dimensional sphere that you can rotate and zoom. On the globe, great circle routes appear as they truly are—arcs along the surface of a sphere. This is the most physically accurate representation and helps build intuition for why routes curve the way they do. Spinning the globe to view routes from different angles can reveal patterns that aren't obvious on flat maps.
Satellite and terrain views overlay your routes on actual geographic imagery. You can see exactly which countries, mountains, oceans, and cities your flights passed over. This contextualizes the abstract lines on a map with real-world geography and can trigger memories of looking out the window during the flight.
Different projections highlight different aspects of your travel patterns. Mercator is good for understanding routes in terms of conventional geography. Globe view helps understand the physical reality of distance on a sphere. Switching between projections as you explore your flight history gives you a richer understanding of where you've been and how you got there.
For the curious, here's a brief look at how great circle distance is actually calculated. You don't need to understand this math to use Jetmap—the platform does it automatically—but knowing what's happening under the hood explains why the numbers are what they are.
Great circle distance uses the haversine formula, which calculates distance between two points on a sphere given their latitudes and longitudes. Without getting too deep into trigonometry, the formula accounts for the curvature of the Earth to give you the actual shortest distance along the surface.
For example, Sydney (33.9° S, 151.2° E) to Los Angeles (34.1° N, 118.2° W) by great circle distance is approximately 12,050 kilometers. If you naively calculated the difference in latitude and longitude and converted to distance, you'd get a very different (and wrong) number because that approach doesn't account for the spherical surface.
When Jetmap shows you total distance flown, it's summing these great circle distances across all your flights. This gives you a meaningful measure of how far you've actually traveled through the air. Your total distance flown is the actual physical distance your body has moved through three-dimensional space aboard aircraft following great circle paths around the globe.
Understanding great circle routes isn't just trivia. It matters practically when you're building a complete picture of your aviation history:
Accurate distance tracking: Great circle distance is the standard way distances are measured in aviation. When airlines publish flight distances, when frequent flyer programs calculate miles or kilometers for earning, when fuel calculations are done, they're all based on great circle distance. If your flight tracking platform used any other distance calculation, it wouldn't align with official flight distances.
Realistic visualization: When you see your flights mapped with curved great circle arcs, you're seeing a representation of the approximate paths aircraft actually followed. This is more meaningful than straight-line connections between cities, which would be physically impossible to fly.
Understanding time in air: Great circle distance also helps explain why some flights take the time they do. A flight from Perth to London is over 14,000 kilometers by great circle distance—that's why it takes nineteen hours. The distance on a map might not convey that scale intuitively, but seeing the great circle arc that spans half the globe makes the time airborne understandable.
Appreciating route efficiency: Looking at your great circle routes shows how efficiently modern aviation connects distant points. The curved path from Sydney to London might pass over thirty countries, but the aircraft follows the optimal route to minimize flight time. Every one of your long-haul flights represents a carefully planned great circle path (or close approximation) refined over decades of aviation experience.
Great circle routes are one of those concepts that seems simple once explained but reveals something profound about navigation, geography, and how our mental maps of the world aren't always accurate representations of physical reality. The shortest path between two points on a curved surface doesn't follow what looks straight on a flat map. Our intuitions, trained on flat surfaces, mislead us when we look at global-scale navigation.
For aviation enthusiasts and frequent travelers, understanding great circles enriches how you think about your flight history. Every route you've flown followed (approximately) this optimal path. Every hour in the air was spent traversing an arc across Earth's surface that represents the shortest way to get there. The curves you see on your Jetmap flight map aren't decorative or arbitrary. They're the footprints of great circle navigation across a spherical planet.
Next time you're on a long-haul flight and the moving map shows the aircraft tracking a curved path that seems to go miles out of the way, remember: that curve is the straight line, and what looks straight on the map is actually longer. It's a reminder that we live on a sphere, and aviation is one of the few times in daily life when that fact matters viscerally.
So embrace the curves. They're the signature of efficient global aviation and the physical reality of traveling through three-dimensional space on a planet that refuses to be perfectly represented on any flat map. Your flight history isn't a collection of straight lines. It's a web of great circle arcs spanning the globe—and that's much more interesting.
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