Here's the real reason planes fly faster going east than west

20.03.2024 - 15:27 / thepointsguy.com / El Niño / Airlines

If you've ever taken a westbound flight, you may have noticed the flight time was shorter coming home than on the way there. For example, a direct flight from New York to Los Angeles takes about six hours and four minutes. However, you shave about an hour off the flight time on the return flight, which clocks in at just five hours and eight minutes.

If you look at flight times for a transatlantic flight, the time savings can increase even more: A flight from San Francisco to Hong Kong, for example, clocks in at about 14 hours and 45 minutes, but coming back takes around 12 hours and 35 minutes.

Related: Why the quickest flight route might not always be the obvious one

This discrepancy in flight times has nothing to do with the earth's rotation, time zones or any other theories you may have heard. Strong air currents that flow from west to east at high altitudes, called jet streams, are the actual cause.

TPG spoke with aviation and meteorology experts to learn about jet streams, how they affect flight times and how pilots utilize them when planning their flight paths.

According to the National Oceanic and Atmospheric Administration, jet streams are "relatively narrow bands of strong wind in the upper levels of the atmosphere, typically occurring around 30,000 feet (9,100 meters) in elevation."

"Jet streams exist because of temperature contrasts," Marc Weinberg, chief meteorologist at WDRB in Louisville, Kentucky, told TPG. Jet streams form at the boundaries between warm air and cold air.

They flow from west to east but can shift from north to south based on air temperature. "Jet streams will always form over the largest temperature contrast," Weinberg explained. "Winter pushes the jet streams south as the cold air moves south, and as temperatures warm up in the summer, they push farther north again," he added.

In winter, you will typically see stronger jet streams because the more pronounced difference between the hot and cold air boundaries causes the intensity of the jet stream to increase. Other climate patterns, like El Nino and La Nina, add to this intensity.

There are several jet streams — or jets — across the globe: two polar jet streams near the North and South poles and two subtropical jet streams closer to the equator, according to the NOAA.

Because the air inside a jet stream moves faster than the air around it, planes traveling through the stream get a speed boost.

"On average, the jets usually move at about 110 or 120 miles per hour," Amanda Martin, acting warning coordination meteorologist for the Aviation Weather Center, told TPG. A plane flying within that jet stream will move faster, as demonstrated in the above examples between New York and LA or San Fransisco and Hong Kong.

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