Delays are a fact of life at New York’s three main airports.

Each day, thousands of passengers are stuck on planes at the airports — Kennedy, La Guardia and Newark Liberty International — sitting in line behind a dozen other planes waiting to take off or circling overhead until they get clearance to land.

And the delays persist, despite changes in procedures and schedules by the airlines, airports and Federal Aviation Administration over the years. (In the latest move, the F.A.A. last fall created new flight paths out of Kennedy to speed up departures.) Even a significant drop in the number of flights since the economy slowed has not helped much. Flight delays last year in New York were as bad as they were five years ago.

In the first half of 2011, the region’s airspace — defined as the big three airports, plus Teterboro Airport in New Jersey, which caters to corporate jets, and Philadelphia International Airport — handled 12 percent of all domestic flights but accounted for nearly half of all delays in the nation. In the same period in 2005, they represented just a third of all delays, according to a report by the Government Accountability Office.

These delays ripple across the country. A third of all delays around the nation each year are caused, in some way, by the New York airports, according to the F.A.A. Or, as Paul McGraw, an operations expert with Airlines for America, the industry trade group, put it, “When New York sneezes, the rest of the national airspace catches a cold.”

Delays come from a variety of causes, including mechanical problems with planes, late crews, missing passengers or misplaced bags. In many cases — though the exact share is impossible to estimate precisely — weather plays a big role. Snow or fog can ground planes for hours in the winter, while summer storms frequently send airline schedules into disarray.

According to the Department of Transportation, a flight is considered on time if it leaves or arrives at its gate within 15 minutes of its schedule. But even that statistic can be misleading. To minimize late arrivals, airlines have long padded their schedules, counting flight times as longer than necessary. One study, by the Senate Joint Economic Committee, concluded that huge delays in 2007, which affected 320 million passengers, cost the economy $41 billion that year. That figure includes losses to the airlines, wasted time for passengers and the overall cost to the economy.

The New York area airports, of course, are not the only ones that suffer from chronic delays, but they are consistently ranked among the worst in the nation. According to the report by the G.A.O., 80 percent of all delayed flights late in 2009 happened at just seven airports — La Guardia, Kennedy, Newark, San Francisco, Atlanta, Philadelphia and O’Hare in Chicago.

At Kennedy, a quarter of all flights did not leave on time in the first 10 months of 2011, the latest period of data available, with delays averaging 67 minutes. That is up from 58 minutes in 2006. Similarly, in Newark, more than a quarter of all flights did not leave on time, and just 66 percent arrived on time, according to data from the Bureau of Transportation Statistics. That was the worst performance of all the major airports in the nation last year.

The region’s challenges are unique and daunting for air traffic managers. There are four airports within a 30-mile radius, heavy traffic and little room to build a new runway anywhere convenient. Complicating matters further, such proximity means that what happens at one airport has an effect on the operations of the other airports.

A change of winds at Kennedy, for instance, can affect what runway is used at La Guardia so that planes heading into either airport do not cross paths. In turn, that can affect how traffic is directed into Newark Liberty and Teterboro.

“You have to think about it as one giant airport,” said Robert Maruster, the chief operating officer of JetBlue Airways, one of the top operators at Kennedy Airport.

To address this chronic problem, which goes back decades, the F.A.A. has set up a system of quotas, called slots, at the New York airports that effectively limit airlines from scheduling more flights than airports can handle — a cause of widespread delays in previous years. As part of a decade-long redesign of the region’s airspace, the F.A.A. is also seeking to smooth traffic flows among the airports so that flights landing at Kennedy do not restrict departures at La Guardia. Last October, it introduced a new takeoff route out of Kennedy — which it calls the “J.F.K. wrap” — that takes planes headed west on a northern loop over Nassau and Westchester Counties before sending them onto the traditional highways in the sky that guide planes to cities like San Francisco or Denver.

The wrap, which avoids more congested airspace south of the airport, is meant to get flights out of the Kennedy airspace faster and reduce delays in the process. Airlines, however, are unenthusiastic because the route forces them on a slightly longer flight, which raises their fuel bill.

“Managing air traffic in and around New York is challenging because so many aircraft want to fly there and the airports are so close together,” David Grizzle, the F.A.A.’s air traffic chief operating officer, said in a statement.

Improvements have also been made on the ground. The Port Authority of New York and New Jersey, which owns the New York airports, recently expanded one of Kennedy’s four runways and added more taxiways so that airplanes can get on and off the runways faster.

It also set up a program that provides departing airplanes a more precise time frame to leave their gate so they can reduce their time on the taxiways, and cut delays before takeoff.

But after all that has been done to reduce delays, the biggest drop has been because of the airlines’ reductions in the number of scheduled flights since 2007. They have also switched from frequent flights with smaller planes to fewer flights on larger ones. Last year, 81 percent of the domestic flights departed on time, according to the Department of Transportation.

Some airports are building more runways to increase takeoff and landing capacity. In recent years, new runways have been built in Seattle, Charlotte, Chicago and at Dulles International in Washington. Philadelphia has planned an expansion that would add a fifth runway. That plan, however, is being challenged by US Airways, the airport’s biggest operator, which fears its investment in the project would be too high.

Chicago once had the worst airspace in the country. But after O’Hare completed a 3,000-foot extension of its busiest runway in 2008, the airport experienced the largest drop in delayed flights among the nation’s top airports. The new runway enabled O’Hare to accommodate 9 percent more flights than the previous summer, which meant 16 more hourly arrivals in optimal weather. In poor weather — the litmus test for any airport — O’Hare can land 84 planes an hour, compared with the 68 to 72 before the new runway.

On-time departures from O’Hare jumped to 77 percent in 2010 from 68 percent in 2008. The airport is building another runway, which it plans to complete by the end of 2013. It will be able to accommodate larger planes, and further cut congestion. Even so, the airport still ranks as having among the most delays in the nation.

One measure that could help is increasing the use of more precise navigation tools like GPS to fly more direct routes. Those procedures, part of a wholesale modernization of the nation’s airspace over the next decades, will eventually give air traffic controllers a much better picture of where airplanes are flying and allow them to fly closer together. According to the F.A.A., this technology will also allow the system to operate as smoothly in bad weather as in good. In New York, the F.A.A. is about to start testing new arrival and departure routes at both La Guardia and Kennedy that would require airlines to perform more precise landing routes.

“There is a lot of wasted space that has to be factored in because of safety,” said Susan M. Baer, the director of aviation at the Port Authority.

“Radar is not as precise as GPS. You can be in a cab in Manhattan with GPS and you are dealing with more sophisticated technology than is being used by the F.A.A.”

(Source: NY Times)