By Rajesh Kumar Singh and Doyinsola Oladipo

NEW YORK, Jan 22 (Reuters) - U.S. airlines have rolled out sweeping travel waivers as Winter Storm Fern, forecast to spread heavy snow, sleet and dangerous ice across two dozen states, threatened to disrupt air travel across a wide swath of the country heading into the weekend.

The National Weather Service has warned that the mix of freezing rain, sleet and snow could make travel dangerous and lead to power outages and tree damage in parts of the Southeast, while heavier snow is expected farther north. The winter storm is expected to bring cold temperatures not seen since 2021, according to AccuWeather.

Carriers said the mix of ice, snow and strong winds could slow airport operations, ripple into delays and cancellations, and complicate rebooking during one of the busier winter travel periods.

MAJOR AIRLINES OFFER FLEXIBLE REBOOKING OPTIONS

Southwest Airlines LUV.N said it expects disruptions across parts of the South and East, giving customers flexibility to rebook or travel standby within a two-week window. Delta Air Lines DAL.N said weather could affect flights across the Southern Plains and Southeast, including its Atlanta hub, and offered fee-free changes for eligible customers who adjust travel within the carrier’s waiver terms.

American Airlines AAL.O expanded similar flexibility across a network that includes major hubs such as Dallas-Fort Worth and Charlotte, while United Airlines UAL.O issued a waiver spanning much of the Mid-Atlantic and Northeast and parts of the Carolinas and Ohio Valley, including its Newark and Washington-area operations, allowing affected customers to shift travel within a set period without change fees or fare differences if they keep the same itinerary and cabin.

JetBlue JBLU.O issued a Northeast-focused waiver that covers New York and Boston-area airports and said it will waive change and cancel fees for customers traveling to and from 11 cities. Ultra-low-cost-carrier Frontier Airlines ULCC.O said if flights are canceled or delayed for more than three and six hours for domestic and international flights respectively, travelers can request a refund. Spirit Airlines FLYY.PK said it is waiving modification charges and fare differences across 13 cities for travel between January 23 and 25.

Airlines urged travelers to monitor flight status closely and use mobile apps and airline websites for the fastest rebooking options as the storm advances.

(Reporting by Rajesh Kumar Singh in Chicago and Doyinsola Oladipo in New York; Editing by Louise Heavens)

((doyinsola.oladipo@thomsonreuters.com; +1 8623846440))