Passengers on British Airways Flight 112 from Kennedy International Airport in New York to Heathrow Airport outside London received good news early Thursday morning. The flight, which would normally have taken about six hours, was scheduled to arrive 50 minutes early.
Other flights heading east across the Atlantic this week arrived ahead of schedule, in some cases up to an hour earlier, thanks to a jet stream blowing in their favor.
A United flight that took off from Newark Liberty International Airport on Tuesday evening, for example, arrived at Charles de Gaulle Airport near Paris 58 minutes early, a flight that normally takes around seven, according to FlightAware, a website that tracks air traffic lasts hours.
An Emirates flight on Tuesday from Dallas Fort Worth International Airport to Dubai in the United Arab Emirates was scheduled to take 13 hours 44 minutes. According to FlightAware, it landed 57 minutes early.
Here’s what you need to know about these early arrivals.
What is a jet stream?
According to the National Oceanic and Atmospheric Administration, a jet stream is a band of strong winds that blow from west to east in the upper layers of the atmosphere, or about 30,000 feet above the ground.
According to Jennifer Stroozas, a meteorologist at the National Weather Service’s Aviation Weather Center, one way to understand how a jet stream might affect flights is to imagine a boat on the water.
“The atmosphere behaves a lot like a liquid,” she said. “When the water is calm, a boat stays calm. When the water has a strong current, it naturally pushes a boat forward.”
When planes fly in a jet stream, strong winds can propel the plane faster, Ms. Stroozas said.
According to Richard Levy, an aviation consultant who used to fly commercial aircraft, commercial flights typically fly at a speed equivalent to ground speed of about 570 miles per hour.
The jet stream over the Atlantic has contributed to flights traveling faster than their average speed this week. For example, the British Airways flight from New York to London reached a speed of 734 miles per hour
Jetstream-based flights are not uncommon.
Kevin Kuhlmann, a professor of aerospace sciences at Metropolitan State University of Denver, said it was common for jet streams to accelerate flights from west to east.
In summer it is more common for flights further north to be affected by a jet stream. In winter, the jet stream can shift south, said Kuhlmann.
That shift “could lead to a situation where traffic increases,” he said.
Jetstream-based flights are not limited to flights across the Atlantic. Mr. Levy said he was used to jet streams speeding things up as he flew east over the Pacific Ocean.
Jet streams can also increase the speed of domestic flights. A jet stream that blew across the United States in February 2019 caused eastbound flights to arrive significantly ahead of schedule.
Turbulence can be a problem.
The air currents are not always a blessing for pilots and travelers, experts said. Flying through a jet stream can cause turbulence in some cases.
To avoid problems with turbulence, pilots sometimes fly at a lower speed, Levy said. He said flying through a jet stream can be like driving on a bumpy road.
The faster someone drives on a bumpy road, “the worse it is for the car and for you,” Levy said, adding that in such situations it’s better to drive slower.
“That’s exactly what we do with turbulence,” he said. “We’re bringing it back.”
According to Kuhlmann, pilots most often encounter turbulence when entering and exiting the jet stream.
“This transition area will definitely present the possibility of turbulence,” Mr. Kuhlmann said. “But just being in it doesn’t mean it’s dangerous.”
Still, turbulence can be a problem on any flight, jet stream or no jet stream, Mr. Levy said. Pilots remind passengers to wear their seatbelts to keep them safe, and they stay in touch with air traffic controllers who can warn them of possible turbulence.
The return flight may not be as quick.
Airplanes flying west to east can be favored by strong easterly winds, but the same current can have the opposite effect on an aircraft flying west.
“The opposite is also true,” Ms. Stroozas said. “If it flies into a strong wind it would effectively slow it down, just like trying to paddle upstream.”
It is possible to avoid flying west into a jet stream, Mr. Levy said, because “A, it slows you down; B, you’ll burn gas like crazy with nothing in sight; and C, the turbulence.” Sometimes it is unavoidable given the flight route, he said.
On a westbound flight from London to New York City, Mr. Levy said the jet stream could be largely avoided by flying north over Greenland.
“We’re not getting close to it,” he said.
Arriving early is not always best.
Arriving at your destination early is usually good news.
“I’d like to get in early at O’Hare in Chicago,” Mr. Kuhlmann said.
He added: “But you know what? “There is no gate for you” if you land the plane too early.
The potential problem: Passengers may be stuck on the ground of the plane while the crew waits for a gate so everyone can disembark.
Mr. Levy said waiting for a gate was less disruptive for travelers at some airports in Europe where gates are reserved for certain airlines. Flight tracking computers also help avoid delays on the ground.
“Once the wheels are off the ground,” he said, “the computer immediately knows how long you’re flying.”