Passengers who were on British Airways’ Flight 112, from Kennedy International Airport in New York to Heathrow Airport outside London, received some good news early Thursday morning. The flight, which normally would have taken about six hours, was going to arrive 50 minutes early.
Other flights traveling east over the Atlantic Ocean this week have been arriving ahead of schedule, up to an hour early in some cases, thanks to a jet stream that has been blowing in their favor.
A United flight that departed from Newark Liberty International Airport on Tuesday night, for instance, arrived 58 minutes early at Charles de Gaulle Airport near Paris, a flight that normally takes about seven hours, according to FlightAware, a site that tracks aviation traffic.
An Emirates flight on Tuesday from Dallas Fort Worth International Airport to Dubai in the United Arab Emirates was supposed to take 13 hours 44 minutes. It landed 57 minutes early, according to FlightAware.
Here’s what you need to know about these early arrivals.
What’s a jet stream?
A jet stream is a band of strong winds blowing from west to east in the upper levels of the atmosphere, or about 30,000 feet from the ground, according to the National Oceanic and Atmospheric Administration.
One way to understand how a jet stream could affect flights is to think about a boat on water, according to Jennifer Stroozas, a meteorologist with the Aviation Weather Center at the National Weather Service.
“The atmosphere behaves a lot like a fluid,” she said. “If the water is calm, a boat will also remain still. If the water has a strong current, it will naturally push a boat along.”
When planes fly within a jet stream, strong winds can push the plane along faster, Ms. Stroozas said.
Commercial flights typically fly at a speed equivalent to a ground speed of about 570 miles per hour, according to Richard Levy, an aviation consultant who used to fly commercial aircraft.
The jet stream over the Atlantic this week has been helping flights go faster than their average speeds. The British Airways flight from New York to London, for example, reached a flying speed of 734 m.p.h.
Jet-stream-aided flights aren’t rare.
Kevin Kuhlmann, a professor of aviation and aerospace science at the Metropolitan State University of Denver, said that it was common for jet streams to speed up flights traveling from west to east.
In the summer, it’s more common for flights to be affected by a jet stream when they are farther north. In the winter, the jet stream can shift south, Mr. Kuhlmann said.
That shift “could create a situation where it’s given a boost to that traffic,” he said.
Jet-stream-aided flights aren’t limited to those that cross the Atlantic. Mr. Levy said he was used to jet streams speeding things up when he was flying east over the Pacific Ocean.
Jet streams can also increase the speeds of domestic flights. A jet stream that was blowing over the United States in February 2019 helped eastbound flights arrive well ahead of schedule.
Turbulence can be an issue.
The air currents aren’t always a boon to pilots and travelers, experts said. Flying through a jet stream can create turbulence issues in some instances.
To avoid problems with turbulence, Mr. Levy said, pilots will sometimes travel at a lower speed. He said that flying through a jet stream could be like driving on a bumpy road.
The faster someone drives on a bumpy roadway, “the worse it is for the car and for you,” Mr. Levy said, adding that in those situations it’s better to slow down.
“That’s exactly what we do with turbulence,” he said. “We bring it back.”
Pilots encounter turbulence most often when traveling in and out of the jet stream, Mr. Kuhlmann said.
“That transition area is definitely going to have the possibilities of turbulence,” Mr. Kuhlmann said. “But just being in it does not 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 keep their seatbelts fastened so they can be safe, and they stay in contact with air traffic controllers who can alert them about the possibility of turbulence.
Flying back may not be as fast.
Planes traveling from west to east can be aided by strong easterly winds, but the same current can have the reverse effect on a plane going west.
“The opposite is also true,” Ms. Stroozas said. “If it flies into a strong wind, it would effectively slow it down, also like trying to paddle upstream.”
It’s possible to avoid flying west into a jet stream, Mr. Levy said, because, “A, it slows you down; B, you’re going to burn gas like crazy with nothing in sight; and C, the turbulence.” At times, it can’t be avoided, given a flight’s route, he said.
On a westbound flight from London to New York City, Mr. Levy said, the jet stream can largely be avoided by flying north over Greenland.
“We don’t go anywhere near it,” he said.
An early arrival isn’t always best.
Arriving at a destination ahead of schedule is usually good news.
“I’d love to be getting into Chicago’s O’Hare early,” Mr. Kuhlmann said.
He added: “But then guess what? There’s no gate for you” if you land the plane too early.
The potential problem: Passengers might find themselves sitting in the plane, stuck on the ground while the crew waits for a gate so everyone can deplane.
Mr. Levy said that waiting for a gate was a less common annoyance for travelers at some airports in Europe, which have gates dedicated to certain carriers. Flight-tracking computers also help avoid delays on the ground.
“As soon as wheels are off the ground,” he said, “the computer instantaneously knows what your flight time is.”