# Why your flight path curves on the map

> The straightest route on a globe looks bent on a flat map. Then wind, rules and traffic pull the real flight off that line. With numbers for real routes.

By Derek Johnson. Updated Nov 7, 2026. Source: https://skycapapp.com/articles/window/why-flight-paths-curve/

Your flight path curves on the map because the map is flat and Earth isn't. The shortest line between two cities is an arc around the globe, called a great circle, and most flat maps draw it as a bend. New York to Hong Kong by the straight line on a wall map is about 10,160 miles. By the great circle it's about 8,060, and that route passes within 6° of latitude of the North Pole.

That's the first bend. The flight you're on has usually picked up a few more.

## Take a string to a globe

Stretch a string tight between two cities on a globe and it shows the shortest route. For cities at similar latitudes in the north, it swings poleward, because that's where the circles of latitude are small and the distance across is short. The flat map stretches those high latitudes so much that the shortcut looks like a detour.

The saving grows with distance and latitude. Here's the comparison with the straight line on a standard Mercator map, using great-circle distances between the airports:

| Route | Straight on the map | Great circle | Saved | Northernmost point |
|---|---|---|---|---|
| Chicago to Denver | 887 mi | 886 mi | 1 mi | 42°N |
| New York to Los Angeles | 2,494 mi | 2,470 mi | 24 mi | 41°N |
| New York to London | 3,579 mi | 3,443 mi | 136 mi | 54°N |
| Los Angeles to London | 6,048 mi | 5,444 mi | 604 mi | 62°N |
| Chicago to Tokyo Haneda | 7,135 mi | 6,292 mi | 843 mi | 63°N |
| New York to Hong Kong | 10,159 mi | 8,061 mi | 2,098 mi | 84°N |

On a domestic flight the curve is real and doesn't save much. Heading from New York, the great circle to Los Angeles starts at about 274° and ends at about 246°. That swing is why a sunset you'd expect on the left [can turn up on the right](/articles/window/which-side-for-sunset/).

## Wind bends it next

Airlines don't want the shortest route. They want the quickest and cheapest, and the air is moving. The jet stream blows west to east at speeds that can top 275 mph, so eastbound flights go looking for it and westbound flights try to stay out of it.

The North Atlantic is the clearest case. Traffic there runs in two tides, west by day and east by night, on a set of parallel tracks. Those tracks are redrawn every day to fit where the jet stream and pressure systems are. So your New York to London flight tonight and tomorrow night can take noticeably different lines across the middle of the ocean, and neither may be close to the great circle. On a strong jet stream day, eastbound flights can make a long swing to ride it. That's a big part of why the same flight's line looks different from one day to the next.

## Then rules

A two-engine airliner can't go anywhere it likes. US rules limit twin-engine jets to routes within 60 minutes of a suitable airport unless the airline is approved for longer. Those approvals, known as ETOPS, now stretch that limit by hours, and it still shapes long ocean routes. It's one reason a Pacific crossing can stay closer to Alaska or Hawaii than the arc alone would.

Politics bends routes too. In March 2022 the US closed its airspace to Russian aircraft, and US airlines that used to cross Russia for Asia have flown around it since. On a map of the Arctic, you can see that detour.

## Then everything else

Over the US, the arc gets chopped into pieces. Flights follow published departure and arrival paths near busy airports, and controllers space them out by giving them turns. Storms add more: a line of thunderstorms in the Midwest can put an entire stream of flights on a loop around it. Short flights can look oddly zigzagged because of this, and because the arrival path into a big airport may start well off to one side.

## How to read the line in front of you

Three different lines get called "your route", and it helps to know which you're looking at:

- The great circle is the geometry. Many maps draw this when they have nothing better.
- The filed route is the plan the airline sent in.
- The flown track is where the plane has actually been.

If the line ahead of the plane is a perfect smooth arc, it's usually a guess. If it has corners, somebody filed it. And if your plane has wandered off the line, it's most often weather or air traffic control doing their job.

That matters at the window too. A [landmark list based on the great circle](/articles/window/what-am-i-flying-over/) can be off by a whole side of the plane on a day the track runs 50 miles north. If the bends on your flight have you wondering about the [bumps over the Rockies](/articles/ride/most-turbulent-routes/), that's a wind story as well.

## Where the numbers come from

Distances are my calculations from airport coordinates on a spherical Earth, so treat them as good to within a fraction of a percent. Real flights are longer than either figure.

> If you'd like to see how your own route ran, Play the flight in Skycap replays it from takeoff to landing, with the ride and the view. [See how it works](/app/features/#air)

## Sources

- [ICAO, NAT Doc 007, North Atlantic Operations and Airspace Manual](https://www.icao.int/sites/default/files/EURNAT/Documents/EUR%20and%20Nat%20Docs/NAT%20Documents/NAT%20Documents/NAT%20Doc%20007/NAT-Doc-007-EN-Edition-V.2026-1-Amd-0.pdf)
- [14 CFR 121.161, airplane limitations: type of route](https://www.law.cornell.edu/cfr/text/14/121.161)
- [NOAA, The Jet Stream](https://www.noaa.gov/jetstream/global/jet-stream)
- [FAA, U.S. Will Block Russian Aircraft from Using All Domestic Airspace, March 2022](https://www.faa.gov/newsroom/us-will-block-russian-aircraft-using-all-domestic-airspace)