When booking a trip, have you ever looked at the details of your flight and noticed the difference in flight times depending on the direction of travel? Have you ever wondered why this is the case? Indeed, it’s more than just distance that affects your flight time. Let’s look at how travel direction changes flight duration and why this is the case.
It’s faster to fly east (usually)
Flying from London to New York typically takes aircraft just over eight hours. Meanwhile, the flight from New York to London will take around seven hours. A non-transatlantic example might be a flight between Amsterdam and Singapore. A flight east will take nearly 13 hours while flying west towards Europe will be nearly 15 hours.
A medium latitude journey such as from Dubai to Sao Paulo will have similar results – just over 14 hours flying west, and a little over 15 hours flying east.
This difference in flight duration is noticeable in the southern hemisphere too. A flight east from Johannesburg to Sydney will take just under 12 hours, while flying from Sydney to Johannesburg will take closer to 14 hours. Typically, the longer your trip, the more of a difference you will see between travel directions.
So what’s the reason for this general discrepancy?
Riding (or fighting) jetstreams
The primary reason for the difference in travel times with flight direction is due to the jet stream. This is a high-altitude wind that blows from the west to the east across the planet. Airplanes will into the jet stream at around 30,000 feet and then travel with (or against) these winds.
These currents are formed by atmospheric heating from the sun’s radiation and the earth’s Coriolis force (defined as a rotating object with a force perpendicular to the rotation axis).
Prominent jet streams include the polar stream and subtropical streams, located at 60° and 30° north and south of the equator. The polar stream is more substantial, causing much faster winds than subtropical streams. Indeed, airlines on transatlantic and transpacific routes typically use the polar stream while planning flight paths.
Jet streams accelerated by storms
It was in February of 2020 that a British Airways Boeing 747 set a transatlantic speed record flying east from New York to London in less than five hours. On this particular occasion, an intense weather system known as Storm Ciara was making its way towards the UK.
This storm had an effect on winds at higher altitudes, supercharging the jet stream and sending aircraft towards the British Isles at speeds touching more than 800 miles per hour (nearly 1,300 kilometers per hour). Thanks to this particularly strong jetstream, flight BA112 shaved 80 minutes off its scheduled arrival time.
While particularly slow flights never really make the news, we are reasonably confident that aircraft flying west during that period had some extra time in the air due to some strong headwinds!
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