Which side of
the plane?
Every answer to this online is a rule of thumb that was written for somebody else's route. Put in yours and get the actual geometry: where the sun sits, which way the aurora is, and what you fly past.
Sit on the right. You get about 271 minutes of dark sky at aurora latitudes, and the pole is on that side.
Aurora: this route spends about 271 minutes in darkness above 55° geomagnetic latitude, reaching 69° at its highest. The pole is off the right wing. Nothing can promise you a display, since that depends on solar activity on the night, but that is the window to watch.
Why the usual advice fails
Search this question and you get answers like “sit on the left for the northern lights.” That is true for some routes and exactly wrong for others, because the side depends on the direction you are travelling. Fly Reykjavik to New York and the pole is off your right wing for the whole crossing. Fly the same route in reverse and it is off your left. A single rule cannot cover both.
The same goes for the sun. It is not enough to know where the sun is; you need it relative to the aircraft's heading, and the heading changes continuously along a great circle. A flight that starts with the sun on the right can finish with it on the left without the aircraft ever appearing to turn.
What it works out
- The sun.Solar position is computed along the route and compared with the aircraft's heading at each point, so you get the side it sits on for most of the flight and the share of the flight spent in daylight at all.
- The aurora.The oval is centred on the geomagnetic pole rather than the geographic one, which is why the answer is not simply “north”. The tool reports which side the pole lies on, how long the route spends in darkness above 55° geomagnetic latitude, and the highest latitude it reaches.
- What you fly past. Fifty landmarks are checked against the track, and anything close enough to see is reported with its side, its distance off the track, and roughly how far into the flight it appears.
Common questions
- Which side of the plane is best for the northern lights?
- Whichever side faces the geomagnetic pole, which sits near 80.7° north and 72.7° west, not the geographic pole. On a westbound flight from Europe to North America that is usually the right. Eastbound it is usually the left. The tool works it out for your specific route, because the answer flips depending on which way you are going and how far north the track reaches.
- Which side for Mount Fuji?
- It depends on the route, and on Tokyo departures it is often neither: flights between Tokyo and Osaka or Fukuoka follow the Tokaido corridor and pass within a few kilometres of the mountain, so it appears almost directly below rather than off to one side. On approaches from the Pacific it is usually visible to the north.
- Does the sun really matter that much?
- On a long daytime flight, yes. The sunny side gets hot, the window shade stays down, and half the cabin cannot see out. The tool tells you which side the sun sits on for most of the flight so you can pick the shaded one, or the sunny one if you want the view of the clouds.
- Why do you ask for UTC rather than local time?
- Because working out a local offset needs a timezone database with historical daylight saving rules, and getting it subtly wrong would produce confidently incorrect answers. Asking for UTC is less convenient and more honest. Your ticket shows local time, so subtract your departure city's offset.
- Can it tell me about a specific flight number?
- No. Looking up a live flight number needs a commercial flight data API, and this runs entirely in your browser with no server behind it. Give it the airports and the date instead. The great circle between two airports is a good approximation of the route for this purpose, though real flights deviate for weather, airspace and wind.
- How accurate is this?
- The geometry is exact and the sun position is good to well under a degree, which is far finer than the question needs. The bigger sources of error are that real aircraft do not fly perfect great circles, and that the flight time is estimated from distance rather than a schedule. For deciding between seat A and seat F, that is plenty.
How it works
The route is the great circle between the two airports, sampled at 160 points. At each one the tool computes the aircraft's heading, the sun's azimuth and elevation, and the bearing to the geomagnetic pole, then converts each of those into a side by taking the angle relative to the heading. Landmarks use the signed cross-track distance from the route, which gives both how far off they are and which way to look.
All of it runs in your browser. There is no server, no API key and no request to anyone: the airport coordinates and the landmark list ship with the page, and the rest is arithmetic. That also means it keeps working offline once loaded, which is more useful than it sounds when you are already at the gate.
The honest limitations: real aircraft do not fly perfect great circles, the flight time is estimated from distance rather than read from a schedule, and no tool can tell you whether the aurora will actually appear on the night. What it can tell you is which window to book so that it would be in front of you if it does.