342 city pairs — leaving Seoul for New York, you head north, not east
The only data written down is two numbers per city: latitude and longitude. Distance, initial heading, flight time, time difference and arrival time all follow from them. The Earth is round, so the shortest path between two points is the curve where a plane through the Earth’s centre cuts the surface — a flat map merely draws that curve bent. Flight times are given as a range rather than a single figure, because riding the jet stream and fighting it differ by an hour or two.
Great-circle distance
km
Distance, heading, flight time, time difference and arrival time, all from two numbers per city. Leaving Seoul for New York you head north, not east.
Why the route looks bent on a map
The Earth is a ball and a map is paper. Flattening a ball means stretching something, and the common maps stretch the poles the most. So the genuinely shortest path, a curve near the North Pole, is drawn as a long detour. Flying east along the same latitude from Seoul to New York is much further — heading north is the shortcut.
The outbound and the return differ
The distance is the same in either direction, but the time is not. High over the mid-latitudes runs a strong west-to-east wind — the jet stream — which pushes you going east and blocks you going west. Across the Pacific the gap reaches an hour or two. That is why the times here are a range rather than one number.
The time difference is not one number either
Cities that observe summer time sit an hour apart in July from where they sit in January. That is why Seoul and New York are sometimes 14 hours apart and sometimes 13. Start and end dates differ by country and move from year to year, so this chart does not hard-code a number — it gives both the standard-time and summer-time values.
Measured from city centres, not airports
The coordinates are city centres, so these figures differ slightly from the airport-to-airport distances airlines quote. Airports usually sit tens of kilometres out, which on a route over 10,000 km comes to well under 1%.
How to read it
- The only data is two numbers per city: latitude and longitude.
- Distance comes from the haversine formula — subtracting coordinates would ignore that the Earth is round.
- No two points can be further apart than 20,015 km, half the Earth’s circumference.
- The initial heading changes as you go. A great circle is not a constant-bearing route.
- Flight time is distance ÷ ground speed plus taxi and climb, given as a range because of wind.
- The time difference shifts twice a year with summer time, so both values are listed.
Common questions
Q. Why does the route bend north on a map?
Because that really is shorter. The Earth is a ball and a map is paper; flattening the ball stretches the polar regions most, so the genuinely shortest path near the pole gets drawn as a detour.
Q. Why do the outbound and return take different times?
A jet stream runs west to east high over the mid-latitudes, pushing you eastbound and blocking you westbound. Same distance, but an hour or two apart in time.
Q. The time difference here does not match right now.
That is summer time. Cities that observe it sit an hour differently in July than in January, so this chart gives both values — the standard-time one and the summer-time one.
Q. It differs from the distance my airline quotes.
These coordinates are city centres; airlines measure airport to airport. Airports sit tens of kilometres out, which is under 1% on a route over 10,000 km. Real routes also detour around airspace and along airways.