Jet stream helping planes slingshot across Atlantic Ocean at 800 mph

When Virgin Atlantic Flight 10 took off from New York’s JFK International Airport this week, it was running 1 hour 13 minutes late. But within 23 minutes of takeoff, it was careening over the Atlantic at 803 mph – and still got to London’s Heathrow Airport on time. The reason? Fierce jet stream winds supercharging its speed.

The jet stream is like a river of west-to-east winds in the upper atmosphere. Airplanes use it like a highway. If flights are heading eastbound across the Atlantic, they surf the jet stream, usually shaving an hour or more off their journeys. Westbound flights take longer, since planes are working against the jet stream.

Air traffic controllers monitor the jet stream and tweak transatlantic routes accordingly each day. This time of year, it’s not uncommon for eastbound aircraft to exceed 800 mph.

At peak, the Virgin Atlantic flight got up to 809 mph. But it wasn’t alone.

An Atlas Air cargo flight, operated on a Boeing 747, hit 826 mph as it passed south of Newfoundland. It was flying from Dover, Delaware, to Ramstein, a U.S. Air Force installation in Rhineland-Palatinate, southwestern Germany.

Last January, China Airlines Flight 5116 careened across the Pacific at 826 mph as it zipped from Taipei to Los Angeles, taking advantage of a strong jet stream. A British Airways Boeing 747 flying near Greenland hit 825 mph in February 2020.

There are also reports from February of a few passenger planes crossing the Atlantic at speeds between 830 and 840 mph.

How does the jet stream form?

The jet stream forms as warm air from the equator tries to slide into the polar vortex, a whirlpool of cold air near the poles. Ordinarily, this would allow warm air to just fill in the polar vortex. But remember, the planet is spinning – so the air is flung outward at the exact rate that it’s trying to slide into the polar vortex. (It’s the same reason a dip appears in your coffee when you stir it; as you generate a vortex, you fling the fluid outward at the same rate the coffee wants to fill in your little coffee whirlpool.)

Where is the jet stream strongest?

The jet stream is the strongest over places where surface temperatures change most dramatically over a short distance. Meteorologists call zones of sharp temperature contrasts a “baroclinic zone.” The jet stream usually slices over baroclinic zones, zipping through the air while clashing air masses bring precipitation.

On Tuesday, for example – the same day that Virgin Atlantic flight took off from JFK – it was 35 degrees and snowing in Tallahassee at the same time it was 75 and pleasant in Miami. That’s a distance of just more than 400 miles.

That’s why the jet stream was super strong at the edge of the cold air mass, which settled just off the East Coast on Tuesday night.

When is the jet stream strongest?

This river of winds is strongest during wintertime. The polar regions cool dramatically, but the tropics don’t change temperature much. That’s why the pole-to-equator temperature difference steepens and the jet stream gets stronger.

The jet stream is also strongest at night. When the sun goes down, there’s less warming of the lower atmosphere. During the day, sun-heated air pockets rise and mix into the jet stream, slowing it. That’s not an issue at night – so the jet stream accelerates. This is especially true over the ocean.

There is some research to suggest a warming climate will favor more airplane turbulence in the future.

Did the planes break the sound barrier?

Even though the speed of sound at sea level and room temperature is about 767 mph, the jets did not break the sound barrier.

That’s because their air speed didn’t change. While they were embedded in a 260-mph jet stream, they weren’t cruising through the surrounding air any faster – the air was moving with them. Their ground speed was extra fast, though.

It’s like being on a moving walkway at the airport. You’re not walking any faster, but you’re moving faster because the medium on which you’re standing – the walkway – is also moving.

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Jason Samenow contributed to this report.