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Last update: 7:55 a.m. ET. Next update: by 11 a.m. ET.

The latest winter storm to snarl travel brought flights at the world's busiest airport to a virtual standstill Wednesday and threatened to send delays and cancellations cascading to all corners of the nation.

The threat of winter weather prompted airlines to cancel all nearly all of their flights Wednesday at Atlanta's Hartsfield-Jackson International Airport, The Atlanta Journal-Constitution reports. Airport officials told the newspaper they anticipate only about 300 of the airport's daily schedule of about 2,500 arrivals and departures will operate on Wednesday.

Atlanta airport spokesman Reese McCranie tells the Journal-Constitution that Wednesday's spate of cancellations there are the most aggressive that anyone at the airport can remember.

Nationwide, airlines had canceled more than 5,300 flights since Monday, according to flight-tracking service FlightAware. That figure included a staggering amount of preemptive cancellations: more than 2,400 of Wednesday's cancellations were made by Tuesday evening. For Thursday, more than 800 flights had already been canceled as of 7:50 a.m. ET on Wednesday, according to FlightAware

Most big airlines waived change fees and relaxed rebooking rules for customers ticketed to fly through stormy airports, though the precise details varied by airline.

Hardest hit on Wednesday were Atlanta and Charlotte, with the two hubs accounting for nearly half of the nation's total cancellations as of 7:50 a.m. ET. Atlanta is a hub for Delta while Charlotte is one of US Airways' busiest hubs.

Delta canceled more than 2,000 flights Tuesday and Wednesday. Southwest, along with subsidiary AirTran, operates a busy base at Atlanta, but the company told theJournal-Constitution that it was unsure if it would operate a single flight from the airport on Wednesday.

In Charlotte, about half of Wednesday's flights had been canceled as of 7:50 a.m. ET.

Unfortunately for fliers, the scope of storm-related cancellations was only likely to expand.

Wednesday's problems at busy airports like Atlanta and Charlotte were likely to persist into Thursday. And, adding to fliers' misery, snow and icy precipitation was expected to start overnight in Washington, Philadelphia and New York. Heavy accumulations were possible for those metro areas on Thursday, which – if the forecasts prove accurate – would likely snarl flights at a half-dozen of the nation's busiest airports into Friday.

Those problems were likely to send disruptions rippling to airports across the nation. A flight from Phoenix to Salt Lake City, for example, could become delayed or canceled if the aircraft or crew scheduled to fly it gets bogged down in the snowy south or mid-Atlantic.

And with such a large disruption likely still to come from the storm, it seemed possible that the total number of storm-related cancellations across the nation could reach 8,000 or more by week's end – disrupting the plans of tens of thousands of passengers.

With so many affected passengers, it could take until next week before airlines are able to clear the backlog of fliers knocked off schedule by this round of disruptions.

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