The Tuesday before Thanksgiving was off to a relatively smooth start for air travelers through mid-morning, though the threat of major problems from a developing coastal storm loomed for Wednesday - one of the busiest travel days of the year.
Only about 60 flights had been canceled nationwide as of 10 a.m. ET Tuesday, according to FlightStats. A few dozen delays were being reported at a handful of big airports - though nothing that would be considered extreme by winter-weather standards.
But the approaching Nor'easter could change that once its wind, rain and low clouds begin to affect the busy - and delay-prone - airports in Philadelphia and the New York City area.
Underscoring that concern, four big airlines have already moved to waive change fees for many flights through the Northeast and mid-Atlantic ahead of the approaching Nor'easter.
Delta and US Airways were the first to roll out their weather waivers early Monday evening. They were followed soon after by United and JetBlue. It's likely more airlines will do the same as the storm approaches.
As for the storm, it already created major headaches in Texas earlier this week, forcing American Airlines to cancel nearly 1,000 flights at its Dallas/Fort Worth hub when ice was forecast for North Texas.
Now the same system is set to develop into a coastal storm, with forecasts calling for heavy snow in interior sections of the Mid-Atlantic and Northeast and icy conditions in parts of the Ohio Valley.
The biggest problems for Thanksgiving fliers, however, will likely be the windy, cloudy and rainy conditions forecast to hit delay-prone airports in the Mid-Atlantic, notably Philadelphia and the three big New York City-area airports.
Those airports struggle to maintain normal schedules even in modest weather conditions. A full-fledged coastal storm - which meteorologists are forecasting to develop by Tuesday - could bring major delays and hundreds of cancellations to some of the nation's busiest hub airports just as a crush of Thanksgiving fliers head to the airports.
Nearly every big airline has at least one hub at one of those delay-prone airports in the storm's projected path.
United, the nation's biggest carrier, operates at major hub at Newark Liberty International. No. 2 Delta operates hubs at both New York LaGuardia and New York JFK. American and JetBlue each operate hubs at JFK. One of US Airways' biggest hubs is at Philadelphia. All of those airports can suffer delays - and occasionally spikes in cancellations - just from low clouds or strong winds from directions unfavorable to their runway layouts.
Winds and heavy rains also were forecast for the three busy Washington-area airports Tuesday and Wednesday. However, operations at Washington Dulles, Washington Reagan National and Baltimore-Washington International tend to be more tolerant of poor weather than at the counterparts in New York and Philadelphia.
The interior regions of the Mid-Atlantic and Northeast could see snowfall totals of up to a foot in some areas, though the heaviest snow will mostly smaller airports. The one notable exception: Forecasts call for 5 to 8 inches at Pittsburgh International, though it's a snow belt city accustomed to dealing with snow.
Snow or a wintry mix also were forecast at for airports such as Buffalo, Syracuse and Burlington, Vt., though it was not likely to be enough to affect many flights at those weather-hardened airports. Some smaller airports -- such as Pennsylvania's Erie International -- could see heavy snow totals that are heavy enough to disrupt flights.
The possibility of ice was in the forecast for airports in several states, including Arkansas, Oklahoma Tennessee, western North Carolina and western Virginia. A handful of cancellations had been reported at Oklahoma City's airport, but otherwise no major airline disruptions had been reported in those states as of mid-morning Tuesday.
Two other cities city where the forecast will be closely watched are Atlanta and Charlotte. Atlanta is the world's busiest airport -- and Delta's top hub -- while Charlotte is a major hub for US Airways.
The forecasts in those cities call for rain and generally ugly weather, but those airports seem likely to avoid the problems expected up north. Neither Delta nor US Airways included the cities in their weather waivers -- at least so far.
Airports in western two-thirds of the nation aren't expected to see major weather events in the days leading up to Thanksgiving. But air travel could be affected if problems ripple out of the busy Mid-Atlantic and Northeast. A flight from Phoenix to Seattle, for example, could become delayed or canceled if the flight or crew schedule to operate it gets bogged down by the disruptions to the East.