Federal Aviation Administration spokeswoman Laura Brown said "ground stops" halting air traffic had been lifted at Newark, La Guardia, JFK and Cleveland Hopkins in the United States, but not at the two Canadian airports.
Flights in the air en route to the airports were allowed to land because air traffic control apparatus was operating on backup power.
She said that "as in a severe weather situation," significant disruption would continue for up to 24 hours as the ripple effect from the grounding of dozens of flights moved outward from the affected airports in the Northeast, which has the busiest airspace in the country.
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