flight.gripe

How it works

How is the flight distance worked out?

It's the great-circle distance: the shortest path between the two airports over the surface of the Earth, using a mean Earth radius of 6,371.0088 km. The figure on the WGS-84 ellipsoid (Vincenty's formula) is shown too; the two differ by up to about 0.5%. Planes rarely fly the exact great circle, because of airways, winds and restricted airspace, so the distance actually flown is usually a little longer.

How is the flight time estimated?

40 minutes for taxiing, take-off, climb and landing, plus the distance at an average 850 km/h, rounded to 5 minutes. It's a still-air figure. Eastbound flights across the Atlantic and Pacific often take noticeably less time than westbound ones because of the jet stream, so check the airline's schedule for the real number and type it in above.

Why does the route curve on a flat map?

The shortest path on a sphere is part of a great circle. On a globe it's a straight line, but flat maps stretch the far north and south, so the route looks like an arc bending towards the pole. That's why New York to London passes near Ireland, and flights from the US west coast to Asia pass near Alaska.

How does the jet-lag plan work?

Your body clock has a low point a few hours before you usually wake. Bright light in the hours after that low point moves the clock earlier; light in the hours before it moves the clock later. The plan tracks where your clock probably is each day and tells you when to get light and when to keep it dim, assuming it shifts about 1 hour a day earlier or 1.5 hours a day later. It follows the approach described by Eastman and Burgess (2009). It's general guidance, not medical advice; everyone adjusts at a different pace.

Where does the airport data come from?

About 9,400 airports with IATA or ICAO codes from OurAirports, which is in the public domain. Each airport's time zone is that of the nearest town in the same country in GeoNames (CC BY 4.0), checked against common airports. The map is drawn from Natural Earth (public domain). All of it is served from this site; nothing you type is sent anywhere.

Can it track a live flight?

No. Live flight positions come from commercial data feeds with their own terms, so flight.gripe sticks to what can be worked out on your device. For a time zone without a flight, use timezone.gripe.