Airlines and airports on Friday were preparing for widespread disruptions this weekend as a powerful storm threatened to blanket large parts of the country in ice and snow.

The storm was expected to hit much of the Southern United States on Friday, prompting some targeted flight cancellations. Delta Air Lines had proactively canceled some Friday flights in northern Texas, Oklahoma, Arkansas, Louisiana and Tennessee, but most cancellations were on the weekend.

By Friday afternoon, American Airlines, which is based in Fort Worth, had canceled 19 percent of flights planned for Saturday, while Southwest Airlines, based in Dallas, had canceled 17 percent, according to FlightAware. At Dallas Fort Worth International Airport, about two in three flights scheduled for Saturday were already canceled, according to Cirium, an aviation data firm. Delta also warned of cancellations Saturday in the Midwest and South.

Airlines have an easier time managing around bad weather at a single airport, but this storm is much more dangerous because of its breadth.

“You have a storm that’s going to progress from the center of the country all the way to the East Coast and a very wide swath north to south,” said Bob Mann, an industry consultant and a former airline executive. “The area of impact and the duration of the impact is far longer than the standard weather event.”

This week and next are typically among the slowest of the year, according to Transportation Security Administration airport screening data. As a result, carriers may have more flexibility and resources to respond to disruptions over the weekend.

By Friday, many airlines had waived fees to change weekend travel, allowing customers to postpone travel from or through many major airports in the eastern half of the United States. Carriers encouraged travelers to confirm their flight status before leaving for the airport, and several airlines said they were shoring up resources to better handle the chaos expected in the coming days.

Delta said it expected the storm to affect about 80 cities it flies to. The airline also said it was sending experts from its hubs in colder climates to help with de-icing and baggage support in Southern airports, including those in Atlanta; Birmingham, Ala.; and Nashville.

Preparing to bounce back after a disruption is often as important as managing the disruption in the first place. American said in a statement that it was moving personnel and planes around to be prepared in the storm’s aftermath.

“We’re repositioning aircraft, aligning crew resources and reinforcing staffing at key airports while coordinating with our partners to help minimize disruption and set the stage for a fast, safe recovery,” the airline said.

The most ominous weather forecasts called for ice and a foot or more of snow in some places. In such conditions, airport runways and taxiways have to be plowed for planes to safely move about, and jets often line up to be doused in de-icing fluid to remove and prevent ice accumulation, slowing operations even at airports that are used to such conditions.

That de-icing process is complex and expensive, especially at airports not used to severe winter conditions. But it is essential to flight safety. Even small amounts of ice can affect a jet’s aerodynamics, hindering pilots’ ability to operate various functions. For American, Chicago O’Hare International Airport is home to the airline’s biggest de-icing operation, treating planes 6,000 to 10,000 times every winter.

While airports in the South may not be as familiar with icy conditions, many do deal with them from time to time. Charlotte Douglas International Airport in North Carolina, a hub in American’s network, said it had a fleet of 40 snow-removal, de-icing and maintenance vehicles at the ready. In 2022, Memphis International Airport debuted a de-icing facility that cost more than $300 million.

At airline command centers, teams of experts work around the clock to monitor flights and help manage and resolve problems as they arise. But such work can be especially complicated because displaced planes, crews, flights or customers can have cascading effects.

As flights are delayed, pilots and flight attendants sometimes reach legal work limits, forcing airlines to cancel more flights or call in replacement crews. A flight attendant stranded in, say, Nashville can’t work a flight in Chicago the next day as planned. Poor conditions can also force planes to be diverted and not be available for a future flight they were scheduled for.