By early Monday evening, more than 6,700 U.S. flights through Tuesday had already been scrubbed, according to tracking service FlightAware.com. Most were to or from cities in the storm's path, from Washington through New York to Boston.
And 2,000 flights had been delayed.
Cancellations and delays will spill over into Wednesday, if not longer.
Airlines cancel flights before storms arrive to prevent passengers from driving to the airport and getting stranded in the terminal. Airlines also want to avoid having their planes stuck at snowed-in airports.
Most major U.S. carriers said they would allow passengers ticketed to, from or through the Northeast through Tuesday or Wednesday to change their plans without getting hit by a reservation-changing fee, typically $200.
But stranded travellers could still have extra costs. When weather causes delays, airlines have no legal obligation to find a hotel room or provide meals for stranded travellers, "although they might do so as a courtesy," said George Hobica, founder of the travel website airfarewatchdog.com. He advised travellers to check the terms of the credit card they used to book the trip — some include coverage for hotels and meals when flights are cancelled due to weather.
The National Weather Service predicted that 2 to 3 feet of snow would fall in a 250-mile stretch of the Northeast, including the New York and Boston areas. Philadelphia was bracing for 14 to 18 inches.
The blizzard in the Northeast was having ripple effects for travellers and airports across the country. Despite temperatures in the 70s and just light rain, 60 departures were cancelled at Los Angeles International Airport, many of them bound for New York or Boston. San Francisco and Atlanta's Hartsfield-Jackson airports each had more than 50 departures wiped out.
What some major airlines are reporting:
Will not fly Tuesday in New York, Boston or Philadelphia. Spokeswoman Mary Ryan said the airline would limit operations at Newark, New Jersey, and New York's LaGuardia and Kennedy airports on Monday night and cancel all Tuesday flights at those airports.
Callers were also experiencing long times on hold because of the heavy volume.
American, its US Airways subsidiary and their regional affiliates planned to suspend operations late Monday at LaGuardia, Kennedy, Newark, Boston and Philadelphia and run a "very limited" schedule in the Northeast on Tuesday, said spokeswoman Andrea Huguely.
DELTA AIR LINES
Has already cancelled 960 flights scheduled for Tuesday and expects to shut down at Boston's Logan Airport and offer limited flights at LaGuardia and Kennedy airports, said spokesman Morgan Durrant.
Durrant said Delta might cancel some flights Wednesday morning.
Has already cancelled nearly 50 Wednesday flights, said spokesman Brad Hawkins.
David Koenig can be reached at http://twitter.com/airlinewriter