It seems like it should be simple: take the distance, divide by the speed, done. Real flight time is a little more involved, and the extra pieces are exactly what separate a good estimate from a wrong one. Here is how it actually works.
Planes do not fly in straight lines on a flat map. The shortest path between two points on a globe is a great-circle route, a gentle curve that on a flat map looks like it arcs toward the pole. This is why a flight from New York to Tokyo passes near Alaska. We start by calculating that true great-circle distance between your two airports.
Next comes the aircraft's cruise speed through the air, typically around 450 to 490 knots for a jet airliner. Divide the distance by that speed and you get the time in the air, roughly. A regional jet is a bit slower, a widebody a bit faster, which is why the same route shows different times for different planes.
This is the step most calculators skip, and it is the one that matters most on long routes. The jet stream can add or subtract 100 knots or more of ground speed. A tailwind makes the trip faster, a headwind slower. We adjust the ground speed based on the direction and latitude of your route, so an eastbound flight comes out shorter than the westbound one, the way it really works. More on that in why your return flight takes longer.
Gate-to-gate time is more than time at cruise. There is pushback, taxi to the runway, the climb up, the descent, and the taxi to the arrival gate. We add a fixed allowance for that, which is why our number is a realistic gate-to-gate estimate rather than a bare in-air figure. Airlines pad their published schedules even further to protect their on-time numbers.
All four steps run instantly in the FlightBeat calculator. Pick two airports and you get the distance, the estimated gate-to-gate time with wind included, and a comparison across aircraft types.
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