Last update: 4:15 p.m. ET. 

Air travelers faced flight headaches across much of the East on Friday from the latest potent storm to move through the region. Nearly 900 flights had been canceled by late afternoon and another 4,500 delayed. 

The disruptions came amid unsettled weather Friday from an advancing front. Temperatures soared into the 50s and 60s as far north as New England but were then forecast to plunge to far-below freezing readings by Saturday. Some cities were forecast to see rain give way to snow or ice, though the large cities immediately along the coast were expected to get only rain.

The storm was disrupting flights at a number of busy airports, including the delay-prone airports serving the New York City metro area.

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Most big airlines had enacted flexible rebooking polices for a number of airports, though  the details varied significantly by carrier.

American’s covered more than a dozen airports, all in the mid-Atlantic and New England. The policies in place at each Southwest and JetBlue covered nearly 20 airports stretching from Maine to the Midwest to Tennessee, where Friday’s rain was forecast to give way to sleet and snow.

At Delta and United, the fee-waivers covered only flights at the greater New York City-area airports. However, by including their hubs at Newark (United) and LaGuardia (Delta) and JFK (Delta), the waivers covered connections from many other cities in the region. Frontier, Air Canada, Porter and WestJet were among other airlines that had waived change fees for certain airports in the eastern U.S. 

Flight cancellations and delays already were creeping up Friday morning. More than 550 flights had been canceled nationwide and another 2,300 were delayed as of 12:15 p.m., according to flight-tracking service FlightAware.

So far, the hardest-hit airports were New York LaGuardia (about 210 cancellations) and New York JFK (about 170), as of 4:15 p.m. ET. That accounted for more than 15% of the day's flights at LaGuardia and about 12% at JFK, FlightAware calculated. Other U.S. airports seeing above-average delays and cancellations were Boston, Cleveland, Nashville, Newark Liberty, Syracuse and Washington Reagan National. 

North of the border, problems were also affecting many of Canada's busy airports in Ontario and Quebec. At Toronto's Pearson International -- Canada's busiest and a hub for Air Canada -- about 15% of the day's flights had been canceled and more were delayed. Other big airports, including Toronto Billy Bishop, Montreal and Ottawa, also were hit with schedule disruptions. 

Travelers scheduled to fly on Friday should expect further disruptions across the East Coast, Great Lakes, the Ohio Valley and eastern Canada as the storm moves through. 

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