Passengers traveling on British Airways Flight 112, from Kennedy International Airport in New York to Heathrow Airport outside London, received good news Thursday morning. The flight, which would normally have taken about six hours, was due to arrive 50 minutes early.
Other flights traveling east over the Atlantic Ocean this week have arrived 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 took off from Newark Liberty International Airport on Tuesday night, for example, arrived 58 minutes early at Charles de Gaulle Airport near Paris, a flight that normally takes about seven hours, according to Flight reporteda site that tracks aviation traffic.
The Emirates flight on Tuesday from Dallas-Fort Worth International Airport to Dubai, United Arab Emirates, was scheduled to take 13 hours and 44 minutes. It landed 57 minutes early, according to FlightAware.
Here’s what you need to know about these early arrivals.
What is a jet stream?
A jet stream is a band of strong winds that blow from west to east in the upper levels of the atmosphere, or about 30,000 feet above the ground, according to the National Oceanic and Atmospheric Administration.
One way to understand how a jet stream could affect flights is to think of a ship in the water, according to Jennifer Stroozas, a meteorologist at the National Weather Service’s Aviation Weather Center.
“The atmosphere behaves like a fluid,” he said. “If the water is calm, a boat will also remain still. “If the water has a strong current, it will naturally push the boat.”
When planes fly within a jet stream, strong winds can push the plane faster, Stroozas said.
Commercial flights typically fly at a speed equivalent to ground speed of about 570 miles per hour, according to Richard Levy, an aviation consultant who used to fly commercial airliners.
The jet stream over the Atlantic this week has helped flights go faster than their average speed. The British Airways flight from New York to London, for example, reached a speed of 1,200 km/h.
Jet stream-assisted flights are not uncommon.
Kevin Kuhlmann, a professor of aviation and aerospace sciences at Metropolitan State University of Denver, said it was common for jet streams to accelerate flights traveling from west to east.
In summer, it is more common for flights to be affected by a jet stream when they are further north. In winter, the jet stream can move south, Kuhlmann said.
That change “could create a situation where that traffic gets a boost,” he said.
Jet stream-assisted flights are not limited to those across the Atlantic. Levy said he was used to jet streams speeding things up when he flew east over the Pacific Ocean.
Jet streams can also increase the speed of domestic flights. A jet stream blowing over the United States in February 2019 helped eastbound flights arrive much earlier than expected.
Turbulence can be a problem.
Drafts are not always a blessing for pilots and travelers, experts said. Flying through a jet stream can create turbulence problems in some cases.
To avoid turbulence problems, Levy said, pilots sometimes travel at a lower speed. He said flying through a jet stream could 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 those situations it’s best to slow down.
“That’s exactly what we do with turbulence,” he said. “We will bring him back.”
Pilots encounter turbulence most frequently when entering and exiting the jet stream, Kuhlmann said.
“That transition zone will definitely have chances for turbulence,” Kuhlmann said. “But just because you’re inside doesn’t mean it’s dangerous.”
Still, turbulence can be a problem on any flight, with or without the jet stream, Levy said. Pilots remind passengers to keep their seat belts fastened to stay safe and stay in contact with air traffic controllers who can alert them to the possibility of turbulence.
Flying back may not be as fast.
Airplanes traveling from west to east may be favored by strong westerly winds, but the same current can have the opposite effect on a westbound airplane.
“The opposite is also true,” Stroozas said. “If you fly in a strong wind, it will effectively slow you down, like trying to row against the current.”
It’s possible to avoid flying west into a jet stream, Levy said, because “A, it slows you down; B, you are going to burn gasoline like crazy with nothing in sight; and C, turbulence.” Sometimes, given the flight path, it can’t be avoided, he said.
On a westbound flight from London to New York City, Levy said, the jet stream can be largely avoided by flying north over Greenland.
“We won’t go anywhere near that,” he said.
Arriving early is not always the best.
Arriving at a destination ahead of schedule is usually good news.
“I would love to get to Chicago O’Hare early,” Mr. Kuhlmann said.
And he added: “But guess what then? There will be no gate for you” if you land the plane too early.
The potential problem: Passengers could find themselves sitting on the plane, stuck on the floor while the crew waits for a door so everyone can disembark.
Levy said waiting for a gate was a less common hassle for travelers at some airports in Europe, which have gates dedicated to certain airlines. Flight tracking computers also help avoid ground delays.
“As soon as the wheels leave the ground,” he said, “the computer instantly knows what their flight time is.”