Jet stream gives New York-London flight a recordbreaking boost

Martin Finucane | The Boston Globe | 10 February 2020

Thanks to a powerful jet stream, a British Airways flight from New York to London broke a record, landing Sunday morning after a brief jaunt of 4 hours and 56 minutes.

The jet stream is being scrutinized these days by scientists, who are concerned it is being thrown out of whack by global warming, with drastic impacts on weather patterns. Scientists interviewed Thursday offered varying views on whether changes in the jet stream will also have an impact on airlines and air travelers.

The jet stream is a high-altitude river of air that generally blows from west to east. (In the case of the British Airways flight, it was blowing at more than 260 miles per hour.) The jet stream's location varies from north to south and it can also diverge from being straight to take big swings to the north or south.

"Pilots and airline companies know all about the effect of the jet stream and they often change their routes" based on where it is blowing, said Jennifer Francis, a senior scientist at the Woods Hole Research Center in Falmouth. "They spend a lot of time looking at it."

Planes flying east can hitch a ride on the jet stream, getting a speed boost, while planes flying west avoid flying into it to save time and fuel. In some cases, pilots avoid riding stronger jet streams because they tend to be more turbulent, she said. The winds typically blow much stronger in the winter than in the summer.

She said the British Airways flight had taken advantage of a "very strong jet stream blowing across in the Atlantic in the last few days" that also brought a major storm to Europe.

Researchers, she said, are looking at the role that human-driven changes in the jet stream's pattern may be playing in phenomena such as polar outbreaks, heat waves, and droughts, because the "jet stream is what creates and steers all our weather patterns."

As for air travel, she said, researchers expect the jet stream to slow down, providing a little bit of fuel savings to jets going upwind, but "probably not enough to really matter to air travel."

"No one has shown" that jet stream changes will "help or hurt jet speeds. It's not expected to be a big deal," she said.

Paul D. Williams, an atmospheric science professor at the University of Reading in England, had a somewhat different take. He suggested that the jet stream at lower altitudes may be slowing down, but at 35,000 feet, where airliners fly, it may speed up.

"We certainly expect it to in the future," said Williams. "I've been expecting the record to be broken."

The previous New York-London records were 5 hours 16 minutes, and 5 hours 13 minutes, and the new time has "absolutely smashed" those records, he said. "I think it will be a long time before that record's broken."

Westbound flights will be slowed, but the two won't cancel out so roundtrips will end up taking longer, with more money spent on fuel and more carbon emissions, Williams said in a 2016 study in the journal Environmental Research Letters.

Williams's work has also included a 2019 study in the journal Nature suggesting that turbulence on transatlantic flights will increase due to changes in the jet stream.

Keith Shine, a colleague of Williams's at the University of Reading, said his own research found a smaller impact on flight times than Williams had. "He found a few minutes difference. We found a smaller difference," he said. "We don't see a systematic change."

"My personal view is that this [recordbreaking time] isn't related to climate change. We know if the jet stream gets in a certain configuration - blowing almost directly from New York to London - you will get these fast times," he said. "In my guess, it was as good as it can get."

"This is an evolving area," he noted. "It doesn't mean the story couldn't change in a few years as our models of the atmosphere improve and our understanding improves."