On a clear day, when pilots can see forever, LaGuardia Airport in New York City can handle 80 takeoffs and landings an hour. But far more flights are scheduled during the day.
Chicago's O'Hare Airport can handle 200 planes every hour in good weather, but for 3-and-a-half hours each day, more than that are scheduled.
And just think about how many more flights will be delayed in bad weather, when fewer planes can take off and land but airline schedules aren't reduced.
The Federal Aviation Administration reported Wednesday that so many flights have been scheduled at certain airports that there is no way all of those planes can take off or land on time. The problem is so acute at eight airports that at least three of every 100 takeoffs or landings are delayed by more than 15 minutes.
"The numbers are high," FAA Administrator Jane Garvey said. "People like to travel by air."
The FAA report provides the first calculations of just how many flights 31 major airports can accommodate without delays, and what improvements are necessary to handle a projected 39 percent growth in takeoffs and landings between 2000 and 2012.
The agency has taken some steps to increase the number of flights that airlines can handle without delays by installing new technology, realigning flight paths and rerouting some planes through Canadian air space and through sectors once reserved exclusively for military flights.
Some airports are planning new runways, and FAA officials are trying to speed up construction.
Eight of the 31 major airports - LaGuardia, O'HareNew York's Kennedy, Newark, San Francisco, Atlanta, Boston and Philadelphia - have a disproportionate impact on the air traffic system, the FAA said.
For example, a plane taking off from LaGuardia in the morning flies several different routes during the day. If it's late in the morning, all of those subsequent flights may be delayed.
Some experts say the airlines are scheduling too many flights at peak travel times.
"They're scheduling flights on top of flights on top of flights so they can capture the revenue, but they know there is extremely little, if zero chance that those flights are going to operate in a satisfactory timeframe," said Dean Headley, associate professor of marketing at Wichita State University and co-author of an annual study of airline quality.
Industry officials said the weather, not scheduling too many flights, accounted for most delays.
"It is wrong to simply suppose that ... airlines are involved in some sort of scheduling abuse," said Jack Ryan, acting senior vice president for the Air Transport Association, the trade group for the nation's major airlines, in testimony before the House Aviation subcommittee Wednesday.
Garvey recommended the airlines review their schedules, but said she did not support imposing caps on the number of flights allowed at each airport. "There's a great deal that can be done voluntarily," Garvey said.
Already, Delta has rescheduled some flights at its Atlanta hub, and American has made adjustments so that the same airplanes fly in and out of O'Hare and different planes fly routes that bypass Chicago. This way, delays at O'Hare won't affect, for example, a Dallas to Miami route.
The Transportation Department inspector general is looking at whether airline scheduling practices, among other factors, have contributed to flight delays and cancelations. The inspector general also is studying possible solutions to delays, such as controlling takeoffs and landings, raising landing fees during peak travel times, and giving airlines limited immunity from antitrust laws so they can discuss scheduling among themselves.
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