Flying west takes longer because you’re flying into the jet stream, a river of fast-moving air that flows from west to east at cruising altitude. On an eastbound flight, that same wind pushes you along as a tailwind, shaving significant time off the trip. A flight from London to New York, for example, can take roughly two hours longer than the return trip from New York to London, even though the distance is identical.
How the Jet Stream Works
Jet streams are narrow bands of high-speed wind that circle the globe at altitudes of four to eight miles, right where commercial planes cruise. They flow predominantly from west to east in both hemispheres. According to NOAA, jet stream winds can exceed 275 mph at their peak, though typical speeds are lower and vary by season and location.
The reason these winds blow west to east comes down to how the Earth spins. The planet rotates eastward, and this creates what’s known as the Coriolis effect: moving air gets deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Instead of flowing straight from the poles toward the equator, the air curves into a predominantly westerly flow (meaning it moves toward the east) at mid-latitudes. That curved flow, intensified by the temperature contrast between polar and tropical air, creates the jet stream.
When you fly east, you ride that current like a conveyor belt. When you fly west, you push directly against it. The plane’s airspeed stays the same in both directions, but ground speed, the rate at which you actually cover the distance between airports, changes dramatically depending on whether the wind is at your back or in your face.
Why Earth’s Rotation Isn’t the Direct Cause
A common misconception is that the Earth simply “rotates underneath” a plane, making westbound flights shorter because the ground moves toward you. The Smithsonian National Air and Space Museum offers a useful analogy: imagine jumping straight up while standing on a moving train. You don’t land further back in the train car, because you’re already moving with it. The same principle applies to aircraft. Planes, the atmosphere, and everything in it are already moving with Earth’s rotation. When you take off, you don’t suddenly disconnect from the planet’s spin.
So the rotation doesn’t help or hinder a plane directly. What it does is shape the wind patterns at altitude. The jet stream is the indirect result of Earth’s rotation, and it’s those winds, not the spinning ground beneath you, that create the time difference.
How Much Time the Wind Adds
The difference depends on the route, the season, and how directly the flight path crosses the jet stream. On transatlantic routes between North America and Europe, the gap is typically one to two hours. Flights between East Asia and Europe see similar patterns: westbound flights from China to Europe face persistent headwinds from the polar jet stream, while eastbound flights get a significant push.
The effect is strongest in winter. Because jet streams form where cold polar air meets warmer tropical air, and that temperature contrast is sharpest during winter months, the winds intensify. A westbound flight in January might face considerably stronger headwinds than the same route in July. In summer, the polar jet stream also shifts northward, closer to the U.S.-Canadian border, which can change how much it affects flights on certain routes.
For a dramatic example of what the jet stream can do in the other direction: in February 2020, a British Airways 747 flew from New York to London in just 4 hours and 56 minutes, setting the record for the fastest subsonic transatlantic commercial flight. Storm Ciara, a powerful Atlantic cyclone, had supercharged the jet stream that day, pushing the plane to a ground speed of 825 mph while it remained well below the speed of sound relative to the air around it. That’s roughly 80% faster over the ground than a typical cruising speed. The same flight westbound would have been brutally slow under those conditions.
How Airlines Adapt Their Routes
Pilots and flight planners don’t simply draw a straight line between two airports. They adjust routes daily based on wind forecasts. Eastbound flights are often routed directly through the jet stream’s core to maximize the tailwind. Westbound flights take detoured paths to avoid the worst headwinds, sometimes flying further north or south, adding geographic distance but saving time overall by skirting the strongest winds.
On some long-haul routes, polar paths offer a way to sidestep the jet stream entirely. A flight from North America to Asia, for instance, might arc over the Arctic rather than fight through mid-latitude headwinds. The shortest geographic path between two points on a globe (called a great circle route) often doesn’t align with the fastest path once wind is factored in, so flight plans are a constant balancing act between distance and atmospheric conditions.
Airlines also burn more fuel heading west on jet-stream-heavy routes. More time in the air against a headwind means more fuel consumed, which is one reason westbound tickets on certain routes can sometimes carry slightly different pricing or why planes may carry extra fuel for the westbound leg.
Routes Where the Difference Is Smallest
Not every route shows a dramatic east-west gap. Flights near the equator experience much weaker jet stream influence, since the strongest winds sit at mid-latitudes (roughly 30° to 60°). A flight between tropical cities may show little directional time difference. North-south routes are also largely unaffected, since the jet stream flows laterally rather than along the flight path.
The effect is most noticeable on long east-west routes through the mid-latitudes: transatlantic crossings, flights between East Asia and Europe, and transcontinental U.S. flights. On a short domestic hop, the jet stream still plays a role, but the time difference might only be 15 or 20 minutes rather than the hour-plus gap you’d notice crossing an ocean.