Berlin → Hanoi

Leave at, arrive at

• Depart 09:0000:33 +1 day
• Depart 14:0005:33 +1 day
• Depart 22:0013:33 +1 day

Local departure time plus flight time plus the offset. Computed with the tailwind figure and the standard-time offset.

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 return leg

From this city

To this city

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 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.

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.

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%.