USA TODAY

Airlines are cancelling flights by the thousands and air travel is poised to grind to a virtual standstill across much of the Northeast Friday and Saturday. That's thanks a potentially historic winter storm that's expected to bring blizzard conditions snow that's measured in "feet" to large parts of New York and New England.

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More than 3,000 flights have been canceled since Thursday in the United States, with most of those coming as airports affected by the storm.

Most of cancellations in that tally were announced even before the first flakes fell in the Northeast, highlighting a trend in recent years in which airlines have proactively canceled flights ahead of a big storm instead of trying to operate right up until the worst conditions arrive.

United Airlines, the nation's biggest carrier, said on Thursday night that it had preemptively canceled Friday 900 flights in advance of the storm. Delta, the USA's No. 2 airline, put its total at 740. JetBlue, which has its two biggest hubs at New York JFK and Boston, said Thursday that it had already canceled 640 flights for Friday and Saturday.

Cumulatively, airline so far today have axed about 2,400 flights and roughly another 500 for Saturday, according to flight-tracking service FlightAware. That's on top of about 350 canceled yesterday - again, mostly at airports that saw the first effects of the storm.

Those numbers are likely to grow throughout the day, with blizzard conditions forecast for a number of major airports. Among the airports expected to see such conditions: New York JFK, Newark Liberty, New York LaGuardia, Boston, Hartford, Providence, Manchester (N.H.), Long Island MacArthur and Westchester County (N.Y.).