Winter Storm Fern is causing major disruptions to air travel across the United States, with airlines canceling thousands of flights and issuing travel waivers as the massive weather system threatens to bring dangerous conditions to more than two dozen states.

The storm, which began Thursday (January 23) and is expected to continue through Monday, is forecast to spread heavy snow, sleet, and ice across a 2,000-mile stretch from Texas to the Northeast. The mix of freezing rain, sleet, and snow could make travel dangerous while causing power outages and tree damage in parts of the Southeast.

AccuWeather predicts the winter storm will bring cold temperatures not seen in five years, with Dan DePodwin, vice president of forecasting operations at AccuWeather, warning that "this will likely result in thousands of flight cancellations on Saturday, Sunday and Monday."

DePodwin noted that even locations far from the storm's direct path will feel its effects: "Even in locations far away from the storm, such as the West Coast hubs, Denver, Chicago, and Minneapolis, ripple effects of this widespread travel-halting winter storm will be felt."

Travel booking app Hopper estimates that upwards of 15,000 flights could be delayed because of the storm, noting a 17% increase in travelers adding Disruption Assistance to trips for this upcoming weekend. More than 2,500 flights scheduled for Saturday have already been canceled as of 4:30 p.m. ET, according to FlightAware.

Airlines have warned that the mix of ice, snow, and strong winds could slow airport operations, force delays and cancellations, and complicate rebooking efforts. They're urging travelers to monitor their flight status closely and use mobile apps and airline websites for the fastest rebooking options. Here are some of the measures the major airlines are taking ahead of the storm:

Delta Air Lines has canceled flights at select airports in Texas, Oklahoma, Arkansas, Louisiana, and Tennessee, saying the move seeks to ensure the safety of customers and staff. The airline is automatically rebooking affected passengers onto the next best itinerary and offering flexibility to customers with existing bookings to change their travel with no fees.
American Airlines issued a travel alert covering 34 airports, warning passengers to expect delays and cancellations through the weekend.
Southwest Airlines is offering customers flexibility to rebook or travel standby within a two-week window for flights in the affected regions.
JetBlue issued a waiver for the Northeast covering New York and Boston-area airports and will waive change and cancel fees for customers traveling to and from 11 cities.
United Airlines issued a waiver covering much of the Mid-Atlantic, the Northeast, and parts of the Carolinas and Ohio Valley.
Spirit Airlines announced it is waiving modification charges and fare differences across 13 cities for travel between Friday and Sunday.

Jonathan Porter, AccuWeather Chief Meteorologist, told Newsweek: "Air travel will likely be a nightmare this weekend into early next week. Travel chaos may ensue, making it very challenging for air passengers to make their way to their destinations, perhaps for days on end."

Armstrong & Getty