DALLAS >> 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 delays and cancellations Wednesday in Boston, New York and Washington — 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 since no major airports are in those states.
Weather wasn't the only culprit for travel headaches. A Black Lives Matter protest in Minneapolis blocked roads around the airport and access to one of the two terminals.
There were about 3,600 delays and 300 cancelations by 4 p.m., according to flight tracking site FlightAware. More than 28,000 flights were scheduled for Wednesday and a typical day sees about 150 cancelations 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 the West, and the South and Ohio Valley could see severe storms before Christmas.
Airlines have been helped recently by the El Niño pattern that has brought above-average temperatures to northern states. "We saw that through the Thanksgiving holiday season, and we've seen that through November and December," said Steve Hozdulick, Southwest Airlines' managing director of operational performance.
United posted its lowest flight-cancellation rate ever for a Thanksgiving week, and Southwest had its best on-time performance ever for the day before the holiday, which helps reduce other problems such as lost or delayed bags.
From 9 percent to 19 percent of flights were delayed over the peak five-day Thanksgiving period, according to tracking service FlightAware.com. A year earlier, delays ran between 12 and 31 percent.