Airlines prep for holiday crush

Weathermust cooperate for smooth hauling of millions of passengers.

Airlines are shifting the timing of thousands of flights, even adding dozens of redeyes, as they try to avoid delays while hauling millions of passengers from now through the Christmas weekend.

Success or failure could all depend on the weather and Mother Nature isn’t making it easy on airlines.

Rain and fog in the Northeast caused delaysWednesday morning in Boston, New York andWashington — the busiest part of the country’s airspace. Rain in Chicago and Atlanta caused some delays in those cities too. Severe storms that ripped through Mississippi and Alabama, however, had little impact on air travel.

There were about 2,600 delays and 230 cancellations by 2 p.m., according to flight tracking site FlightAware. More than 21,000 flights were scheduled forWednesday and a typical day sees about 150 cancellations and 4,000 delays.

The catch: flights are extremely full over the holiday period, with most travelers unable to make changes in their schedule.

Airlines expect about 38 million passengers over a 17-day period spanning Christmas and New Year’s, an increase of about 3 percent, according to an industry trade group, Airlines for America. The group says the average flight could be 90 percent full.

Crowds like that mean that any hiccup in the system — delays at a major airport, a technology glitch — can ripple across the country and leave tens of thousands of passengers standing in airport lines.

“The biggest factor is always weather,” said American Airlines spokesman Ross Feinstein.

Back-to-back storms led to more than 4,300 canceled flights around Christmas 2012. This time the Northeast corridor not only should be free of snow and ice, it should be relatively balmy with temperatures on Christmas Day in the 60s from New York to Boston. But rain and snow are forecast through Thursday in parts of theWest, and the South and Ohio Valley could see severe storms before Christmas.