How CabinShade works

CabinShade is a free tool that answers one question: which side of the plane will the sun be on? You give it two airports, a date and a local departure time. It tells you which window seat stays in the shade, and how long the other side spends in direct sun.

The calculation

Route. We draw the great-circle path (the shortest route over the globe) between the two airports, using coordinates for more than 6,700 airports.
Timing. Your departure time is read in the origin airport's own time zone, with daylight saving applied for that date. Flight time is estimated from distance, using typical cruise speeds from about 550 km/h on short hops to 780 km/h on long-haul.
Sun position. We split the flight into 60 equal steps. At each step we compute the plane's position and heading, and the sun's direction (azimuth) and height above the horizon (elevation) with standard astronomical formulas.
Which side. Comparing the sun's direction with the plane's heading tells us whether the sun is on the left or the right of the cabin at that moment. Steps where the sun is below the horizon count as night.
Recommendation. We add up the sunny time on each side and recommend the side with less sun: A for the left window, F/K for the right. If the sun never rises during the flight, any seat works.

What it can't know

Actual routing. Airlines follow jet streams, airways and air-traffic instructions, so real paths drift from the great circle. This rarely changes which side is sunny, but it can on routes that run close to north–south around midday.
Delays. Leaving an hour late moves the sun. Near sunrise or sunset that can matter.
Weather. Above the clouds the sun is almost always out, but low sun can be hidden by haze or cloud tops.
Your aircraft. Window letters and window positions vary by airline and aircraft. See seat letters explained.

Route pages

The route pages run the same calculation for six departure times (6 am to 9 pm local) on the 15th of January, April, July and October. That shows how the answer changes through the day and the year. For a specific flight, the calculator is always more precise.

Who makes CabinShade

CabinShade is built and run by Skunk Devs. It's free to use and needs no account. Found a missing airport, a wrong answer or have an idea? Send us a message. We read every one.