Ben Mutzabaugh

USA TODAY

Last update: 4:30 p.m. ET on Wednesday, Nov. 26.

Flight schedules for this year's busy day before Thanksgiving took a hit before the day even began.

Airlines scrapped more than 210 flights for Wednesday -- one of the USA's busiest air travel days of the year -- all before the clock struck midnight on Tuesday. All told, flight-tracking service FlightAware counted 214 Wednesday cancellations as of 11:50 p.m. ET on Tuesday.

That number grew even more on Wednesday morning, climbing to about 670 as of 4:30 p.m. ET, according to FlightAware.

U.S. carriers have increasingly decided to preemptively cancel flights in recent years when poor weather was forecast to hit busy airports, and that trend appears to be playing out again for this latest storm. Wednesday's preemptive cancellations came as an approaching winter storm threatened to snarl flights at the peak of the Thanksgiving travel rush.

Nearly a third of Wednesday's cancellations came at just three airports: New York LaGuardia, Newark Liberty and Philadelphia. About 15% of Wednesday's entire schedule had already been grounded and another 25% delayed at Newark, LaGuardia and Philadelphia airports as of 4:30 p.m. ET, according to flight-tracking service FlightAware. A number of those cancellations were made Tuesday evening.

Washington Reagan National, Boston, New York JFK, Westchester County, N.Y., Hartford, Conn., and Wilkes-Barre/Scranton were among other airports that had high numbers of cancellations for Wednesday.

All of those airports were in the path of a storm that brought messy weather and strong winds to East Coast's biggest cities. Still, more than 200 of Wednesday's cancellations came even before the first rain drops or snowflakes fell in those cities.

Regional airlines were hit hardest by Wednesday's cancellations. Of the 671 counted by FlightAware as of 4:30 p.m. Wednesday, more than 480 were on regional carriers like Shuttle America, ExpressJet and Republic. Those carriers fly as regional affiliates for the nation's big airlines, including American, Delta and United.

JetBlue had already canceled 38 Wednesday flights, the most among the big "mainline" airlines as of 4:30 p.m. ET on Wednesday. Southwest had 27 Wednesday cancellations, Delta 24, American/US Airways 23 and United 9, according to FlightAware. The numbers for American, Delta and United all are dramatically higher when their regional affiliates are included in the count. Including those affiliates, more than 120 flights had been canceled at each of those three carriers.

Precipitation in the East's big cities began as rain in coastal areas, though snow had mixed with rain by late morning in Washington, New York and Philadelphia. Baltimore and Philadelphia -- though Washington's Dulles airport is far enough west that some accumulating snow was expected.

In anticipation of the poor weather, nearly every big U.S. airline had moved by Tuesday afternoon to waive rebooking fees to cities in the storm's path.