Prayer times are set by the sun: Fajr at dawn, Dhuhr after midday, Asr in the afternoon, Maghrib at sunset and Isha when twilight has gone. On the ground they change slowly from day to day. On a plane they can change by hours within a single flight, because you are moving across the earth faster than the sun appears to. This article explains how that works, why long flights pass close to the poles, what goes wrong with prayer times there, and how the Flight Salah app handles it.
Your prayer times move with the plane
A prayer begins on board at the moment the sun reaches the right position where the plane is at that moment. Neither your departure city’s times nor your destination’s apply in the air.
Flying east you meet the night early, so prayers come sooner than at home. Flying west you chase the sun, so each prayer can be pushed back by hours. On some long flights the same prayer happens twice.
Take a flight from San Francisco to Doha, leaving at 3:50 pm on 2 November and landing 16 hours later. The sun sets on board twice: once over Oregon, about an hour after take-off, and again over the Caucasus, about two and a half hours before landing.
| Prayer | San Francisco time | Doha time | Where the plane is |
|---|---|---|---|
| Maghrib | Mon 4:52 pm | Tue 3:52 am | Oregon |
| Isha | Mon 6:06 pm | Tue 5:06 am | Canada |
| Fajr | Mon 11:09 pm | Tue 10:09 am | near the North Pole |
| Sunrise | Mon 11:24 pm | Tue 10:24 am | near the North Pole |
| Dhuhr | Tue 1:14 am | Tue 12:14 pm | the Barents Sea |
| Asr | Tue 3:10 am | Tue 2:10 pm | Russia |
| Maghrib | Tue 5:33 am | Tue 4:33 pm | the Caucasus |
| Isha | Tue 6:54 am | Tue 5:54 pm | Iran |
Note that Maghrib on board at 4:33 pm Doha time is not sunset in Doha. Doha’s sunset that day is 4:51 pm. It is sunset over the Caucasus, where the plane is at that moment.
Planes fly great circles, not straight lines on a map
On a flat map the shortest route between two cities looks like a straight line. On a globe it isn’t. The shortest path is a great circle, which bends towards the nearest pole. That is why flights from North America to the Middle East or Asia head north over Canada, Greenland and the Arctic rather than across the Atlantic.
San Francisco to Doha is an extreme case: the great circle passes within about 5° of the North Pole. London to New York is a gentler one, peaking at about 54°N. Real flights stay close to the great circle but don’t follow it exactly. Winds, air-traffic routes and safety rules move them, often some way further south on polar routes. So the times are a close guide, not a precise schedule.
Strange things happen near the poles
Above roughly 48° of latitude the sun does unusual things for part of the year, and inside the Arctic and Antarctic circles it can stop rising or setting altogether:
- Polar night (winter): the sun never rises, so there is no sunrise and no Maghrib to calculate.
- Midnight sun (summer): the sun never sets far enough below the horizon, so the twilight that defines Fajr and Isha never happens.
- Prayers bunch together: near the pole the plane crosses lines of longitude very quickly, so local time on board can run several times faster than a clock. Two prayers can start minutes apart. On the flight above, Fajr and sunrise are 15 minutes apart over the pole.
- Riding the dawn: flying west at the right speed, a plane can stay just ahead of dawn for hours, with Fajr only minutes away the whole time.
- The sun goes backwards: a jet flying west above about 57° of latitude moves faster than the sun does, so the sun drifts back across the sky and a prayer can begin twice. On a flight from Doha to San Francisco leaving at 7:50 am, Dhuhr begins over southern Russia (11:33 am Doha time) and Asr over the Russian Arctic (2:10 pm). Then, over the pole, the sun slips back towards morning, and Dhuhr begins again over British Columbia (11:45 am San Francisco time), two hours before landing. From the window, the sun climbs past noon, sinks back towards the east, then climbs to noon again.
The ordinary formulas for prayer times simply break down here. They give missing prayers, or results that make no sense, such as Dhuhr and Asr two minutes apart.
How scholars handle high latitudes
Islamic scholarship has long dealt with places where the usual signs don’t appear, and there are several established approaches:
- Nearest normal latitude (aqrab al-bilad): use the times of the nearest latitude where all the signs still occur normally.
- Middle of the night: Isha no later, and Fajr no earlier, than halfway between sunset and sunrise.
- One-seventh of the night: Isha at most a seventh of the night after sunset, Fajr at most a seventh before sunrise.
The last two only adjust Fajr and Isha. Near the pole, where there may be no sunset or sunrise at all, they don’t help.
What Flight Salah does
Flight Salah uses the nearest normal latitude rule. Beyond a cut-off latitude, north or south, it calculates prayer times as if the plane were at the cut-off latitude on the same line of longitude. The rule is applied in the air and at the airports alike, so the times don’t jump at take-off or landing.
The usual cut-off is 48.5°. That figure suits an 18° twilight angle, but some calculation methods use a deeper angle for Fajr, and in midsummer the sun never sinks that far below the horizon at 48.5°. For those methods the app uses a lower cut-off, keeping a one-degree margin so Fajr and Isha always exist:
| Method | Cut-off latitude |
|---|---|
| ISNA (North America) | 48.5° |
| Muslim World League | 47.6° |
| Karachi | 47.6° |
| Umm al-Qura (Makkah) | 47.1° |
| Egyptian Authority | 46.1° |
When a prayer begins a second time because the sun went backwards, the app shows both and marks the second one again. Which of the two to pray by is a question for a scholar.
To find the times, the app follows the great-circle route at a steady speed between your departure and arrival. It checks every minute of the flight for the moment each prayer begins on board, then narrows that down to the second. It also shows the prayer already in progress at your departure airport when you take off, and the one in progress at your destination when you land, with how long you have left to pray it.
Things to keep in mind
- Use your actual times. Flights are often delayed. Edit the flight with the real departure time and either the flight length or the arrival time, and the schedule recalculates offline.
- Treat the times as a close guide. The real route and speed differ from a perfect great circle, so allow a few minutes either way.
- The rule is a choice. The nearest-normal-latitude rule is one recognised approach among several. If you follow a different ruling, or are unsure, ask a scholar you trust.
Written for the Flight Salah app. Questions and corrections are welcome in the discussion on Reviewsity.