Fewer flights were canceled as a winter storm that scrubbed hundreds of departures over the previous two days eased its icy grip on the Midwest and Northeast.
But icy runways and high winds Thursday caused average delays of several hours in the New York area.
And some carriers were still licking their wounds from the disruptions earlier in the week.
JetBlue Airways Corp. was dealing with irate customers who were stuck on planes for up to 11 hours at New York's John F. Kennedy International Airport on Wednesday. The airline planned to offer refunds and free flights to the stranded passengers.
"It was a horrible situation," JetBlue Chief Executive David Neeleman said on CNBC television. "It's going to certainly impact us and it's going to be many millions of dollars that we're going to lose from this."
JetBlue canceled nearly 200 flights Thursday - about one-third of its schedule - to avoid a repeat. Ground delays at JFK were topping six hours.
"You can't run an operation when every flight is delayed six hours," Neeleman told The Associated Press.
JetBlue and other airlines expected conditions to return to normal by Friday. Still, analysts said airlines would lose some revenue because of all the cancelations this week. Luckily for the airlines, they had enjoyed relatively mild weather for the first six weeks of the year, when demand for air travel is usually a bit slack anyway.
American Airlines, the biggest U.S. carrier, expected to cancel 30 to 40 flights Thursday, many at New York's Kennedy Airport, after canceling more than 700 flights nationwide the previous two days.
Port Authority crews at JFK were struggling to clear runways, said Tim Wagner, a spokesman for American, a unit of AMR Corp. Ice on the runways triggered tighter federal rules about airplane loads at takeoff, which further complicated operations, Wagner said.
Continental Airlines Inc. said only two flights had been canceled due to weather by Thursday afternoon, but there were delays, especially at Newark, New Jersey.
"Operations are rapidly returning to normal," said Continental spokesman Dave Messing. "The main issue we face (Thursday) is winds at our Newark hub."
Strong crosswinds limited the runways that could be used by arriving flights. As a result, delays for incoming flights in Newark and at JFK and New York's LaGuardia Airport averaged more than two hours by Thursday afternoon, according to the Federal Aviation Administration.
A spokeswoman for Delta Air Lines Inc. said the carrier canceled some flights Thursday at New York's Kennedy Airport, but that they were not having a ripple effect on other airports.
"The hope is that we can reposition our aircraft for smooth operations (Friday)," added the spokeswoman, Betsy Talton.
Southwest Airlines reported delays in Philadelphia but normal service at most other points.
"The weather has departed. Our operations are back on track," said Southwest spokeswoman Brandy King. The airline canceled nearly 1,000 flights earlier in the previous two days.
UAL Corp.'s United Airlines reported an unspecified number of cancelations at Chicago's O'Hare Airport and Dulles International Airport outside Washington. The same airports were the scene of many of United's 2,000 canceled flights earlier in the week.
United spokeswoman Megan McCarthy said the airline planned to operate a normal schedule Friday.
AP Business Writers Harry Weber in Atlanta and Dave Carpenter in Chicago, and Associated Press Writer David B. Caruso in New York contributed to this report.
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