Turbulence can make even the most frequent flier a little unnerved or perturbed. And with nearly 240,000 flights expected over the long Thanksgiving weekend, according to the Federal Aviation Administration, at least a few will encounter rough air.

“It almost always starts getting bumpy as soon as we turn off the fasten seatbelt sign,” joked Morgan Smith, a Boeing 737 pilot. “But honestly, almost everything about turbulence is annoying and not dangerous.”

Fortunately, the start of the Thanksgiving weekend is not forecast to be especially bumpy. “There’s nothing extreme in the jet stream,” said Alek Mead, an Alaska Airlines dispatcher. “Only into Friday there could be some thunderstorms in the Gulf Coast, around Houston and Memphis that could affect turbulence.”

To help pilots find “smooth air,” researchers at the National Center for Atmospheric Research developed a forecast model that takes a meteorological measurement of atmospheric turbulence, called the eddy dissipation rate, and forecasts it over an 18-hour period.

The forecast at the top of this article shows the maximum turbulence predicted across all altitudes where commercial planes fly — so an area shown as predicting moderate turbulence could include altitudes of calmer air. Pilots can use tablets in the cockpit to view more specific forecasts showing which areas of turbulence exist at which altitudes, helping them to navigate over, under or around those zones.

“It’s not an exact science,” said Ms. Smith. “But it helps us plan for turbulence during a flight — like having the flight attendants delay service until we’ve passed an area or giving passengers a heads up about possible turbulence during the welcome aboard announcement.”

Airline dispatchers such as Mr. Mead prepare flight plans hours in advance using software with dozens of weather and air traffic sources to try to avoid turbulence-prone zones. During flight, the dispatchers communicate continuously with the pilots and guide them through unexpected bumps. “These models work well, they’re a valuable tool in our pocket. They let us see the big picture, where everything is going to be,” he said.

Aircraft also have sensors that read the G-forces stressing the plane during flight and file reports automatically. These reports get added into a database that other flight dispatchers are monitoring. If turbulence starts to appear in an area, then other planes coming through the same route can start avoiding it.

“To really simplify it, turbulence is basically disturbed airflow,” Ms. Smith said. “When air changes direction or speed, we get some bumps.”

She compared it to being on a boat on the water.

“As the water moves, so does the boat,” she said. “Like water, air is fluid and has the same effect on a plane.”

Occupants may feel a strain on their shoulders. Unsecured objects can be moved. Food service and walking are still possible.

Occupants feel a lot of strain against their seatbelts. There are objects that are not in their proper place. It's difficult to serve food and walk.

Occupants are forced to use their seatbelts. Things are thrown about. It's impossible to serve food and walk.

An aircraft is thrown about and can't be controlled. Structural damage may occur.

Most people encounter only the lowest levels of turbulence, “light” and “moderate,” according to a review of pilot reports.

“I’ve never experienced severe turbulence,” Ms. Smith said. “It’s pretty rare, and many pilots I know either haven’t experienced it or only encounter it once or twice throughout their entire careers.”

Turbulence almost always feels worse than it is, and even official reports can be rather subjective.

“What some passengers have described to me as severe turbulence, where they thought we dropped thousands of feet, was really more moderate with maybe 10 feet of altitude change and a couple of knots of airspeed variation,” Ms. Smith said.

That said, unexpected turbulence does occur, and injuries happen from time to time.

Of the seven million scheduled passenger flights last year, there were six serious injuries reported in the United States last year that were because of turbulence, according to data from the National Transportation Safety Board. So far in 2022, there have been eight episodes in which someone was seriously injured.

“The only thing people should fear from turbulence is possibly spilling their drink on a flight,” Ms. Smith said. “Most injuries from turbulence come from people being out of their seats or not having their seatbelts on when it gets bumpy. So keep your seatbelt fastened, and don’t set your drink on your laptop!”

She has other tips for nervous fliers, including sitting near the front, where the ride is smoother, and flying in the morning. As the day warms into the afternoon, heat rising off the land increases the chance for turbulence near the ground and turbulence caused by storms. She also has advice for younger passengers who might be fearful and have not yet chosen their career path.

“It’s almost always a better ride in the flight deck than the rest of the plane,” Ms. Smith said. “So, if you don’t like the feeling of turbulence, become a pilot!”