U.S. flight cancellations approached 7,000 as United Continental Holdings Inc. joined Delta Air Lines Inc. and JetBlue Airways Corp. in grounding planes ahead of Hurricane Irene's East Coast landfall.

United purged 2,300 flights through Aug. 28, while Delta scratched 1,300 through Aug. 29 and JetBlue scrapped 1,262, spokesmen said. United has a hub at New Jersey's Newark Liberty airport and Delta and JetBlue have bases at New York's Kennedy, which will halt international arrivals at noon tomorrow.

Irene is forecast to plow through the busiest airspace in the U.S., forcing cancellations at seven major airports in Washington, Philadelphia, New York and Boston. New York City's trains, buses and subways will be closed at noon tomorrow, further slowing ground travel for passengers and airline crew.

"I expect this will be a major disruption," said David Swierenga, a former chief economist at the Air Transport Association trade group who now runs consultant AeroEcon in Round Rock, Texas. "You're affecting all the major airports on the northeastern seaboard. The number of flights that they have at those airports per day is very high."

United's schedule reductions include flights for both United and Continental and their regional partners, said Mike Trevino, a spokesman. United, the world's largest carrier, will cease operations tomorrow at all three New York airports and resume the morning of Aug. 29.

Delta's cancellations include its entire New York City-area schedule on Aug. 28, said Anthony Black, a spokesman.

JetBlue, which has its biggest hub at New York's John F. Kennedy airport, will scrap more than 75 percent of its Aug. 28 trips and more than half of its Aug. 29 schedule.

Washington, Norfolk

US Airways Group Inc. said it will cancel 1,166 flights over the next two days, many at Washington-area airports, spokesman Andrew Christie said. American will suspend service at Washington airports for about 24 hours starting at noon tomorrow as 265 flights are erased, said Tim Smith, a spokesman.

Southwest Airlines Co.'s AirTran unit is cutting 265 flights, while Southwest trims 400, spokeswomen said.

The industry's preparations will include relocating planes out of harm's way, a step that minimizes damage while adding to the complexity of resuming normal schedules after a storm.

"They'll be doing a lot of scattering and scrambling," said Robert W. Mann, a former American Airlines executive who owns consultant R.W. Mann & Co. in Port Washington, New York. "That usually means flying the last trip out before the arrival of the storm and not flying in until airfield conditions are able to support it."

Loss Estimates

The storm may cause US$6.5 billion in overall economic losses, according to estimates by Kinetic Analysis Corp. A more easterly track and less intensity puts the company's projected insured losses US$3.1 billion.

The last storm of this magnitude to menace the Northeast was 1985's Hurricane Gloria, which killed 11 people and caused US$900 million in damage. Irene is on a similar track, potentially affecting all six of the largest U.S. airlines, a group led by United, Delta and AMR Corp.'s American.

Kennedy, Newark and New York's LaGuardia form the busiest U.S. aviation market with almost 104 million passengers last year, according to Airports Council International.

Northeast Hubs

Sandwiching that airspace is Philadelphia, where US Airways has a hub and Dallas-based Southwest is the second-biggest operator; Washington, home to Chicago-based United's hub at Dulles airport and a US Airways base at Ronald Reagan National; and Boston, where JetBlue is the largest tenant.

Delays in the area can ripple across the entire U.S. air-traffic control system.

Since Gloria, airlines also have expanded overseas service in New York, so Irene may affect trans-Atlantic routes as well. American and joint-venture partner British Airways began hourly London departures from Kennedy each evening this year.

Irene's approach spurred carriers to begin letting fliers reschedule trips without penalty to and from storm-affected cities, and U.S. airlines canceled about 180 flights yesterday. The tally mounted this week as Irene moved through the Caribbean and the Bahamas.

Dropping fees for changing reservations helps airlines by getting passengers rebooked before any weather disruptions. Carriers typically wait to scrap flights until several hours or a day before storms such as hurricanes or blizzards.

Hub Concentration

The Northeast's concentration of airport hubs makes Irene a bigger threat for cancellations than a storm striking the southeast U.S. or states adjoining the Gulf of Mexico, where hurricanes are common.

Those regions have only two hubs near the coast, Continental's in Houston and American's in Miami. New Orleans, which was ravaged by Hurricane Katrina in 2005, was only the 47th-busiest U.S. airport last year.

Winds and rain may not be airlines' only challenge from Irene. Lack of ground transportation and power failures also may keep airline employees and passengers from getting to airports once the worst of the storm passes, said Mann, the consultant.

Aircraft also are flying with record numbers of full seats, especially at the end of the U.S. summer vacation season, making it difficult for passengers on grounded flights to find new seats after the storm moves through.

Related News:

    U.S. Air Travel Braces for East Coast Storm Shutdown