WARRENTON, Va. — Past rolling hills and grazing horses in this quiet corner of Virginia sits an ultramodern command center that's a pulsating mix of NASA Mission Control, the Counter Terrorist Unit set on the TV show "24" and a stock market trading floor.

Here at the Air Traffic Control System Command Center, run by the Federal Aviation Administration, workers labor every day to keep America's harried summertime air travelers on schedule. Dozens of staffers oversee the nation's airspace to try to minimize those nettlesome travel delays.

Every weekday, roughly 2 million people in the U.S. take to the nation's skies on commercial flights: businessmen looking to seal a deal, families going on long-awaited vacations and fun-seekers jetting off for hedonistic weekends. One objective unites them all: They want to get to their destinations on time. But often that doesn't happen.

The Bureau of Transportation Statistics, part of the Department of Transportation, said the nation's 16 largest air carriers reported an on-time arrival rate of 76.9 percent for June, the most recent month for which statistics were available, meaning that nearly a quarter of flights suffer delays.

According to a Massachusetts Institute of Technology study that analyzed 2007 data and was released last October, delays cost travelers $16.7 billion in lost time and inefficiency — airlines lost $8.3 billion — and took $4 billion off the U.S. gross domestic product.

Michael Boyd, an aviation consultant, said air traffic delays hadn't improved significantly over the past decade despite huge federal investment. He blamed years of what he called bad management at the FAA for continuing congestion and delays, problems that the agency hopes to solve with a new satellite-based air-traffic control system, called NextGen, that's slowly being rolled out.

But Boyd had only praise for the staffers in Warrenton.

"The people at the command center are the ones keeping us safe," Boyd said. "They're keeping airplanes across the sky safe. Those are the people who are real heroes."

Inside an obscure, 3-month-old federal building about an hour's drive from Washington sit banks of flat-screen computers where the center's staff — around 40 people on the eight-hour daytime shift — look for and try to fix potential air travel trouble spots.

The center helps order ground-stop and delay programs to reduce traffic flow to weather-affected airports, warns airlines to reroute planes in advance of weather or other problems and stays in close contact with air traffic control centers across the U.S. to find and resolve other aviation system issues.

Six massive TV screens hang from the wall at the front of the room, displaying weather radar maps, airport configurations, the center's daily schedule, airports that are experiencing delays and news channels.

The original facility in Herndon, Va., was set up in May 1994, when the FAA realized that it had many different centers nationwide looking after specific regions of the country but none that oversaw the entire U.S. airspace.

"Whether it's an equipment outage or a weather issue, we keep the system moving as safely and efficiently as possible," said Mark Libby, the air traffic manager of the center.

"The American public ... can be confident that we'll make the right decisions at the right time to get them to the right place on time," he said.

The center played a key role in the immediate aftermath of the Sept. 11, 2001, terrorist attacks, when the FAA ordered a first-ever halt to all U.S. commercial air travel.

National traffic management officer Michael Murphy, a 10-year veteran of the center and a former controller, was on duty that day and gathered all the call signs of the roughly 30 planes that didn't respond immediately to controllers' communications.

He watched on his computer screens as thousands of planes quickly landed at the closest available airports.

"It was staggering to watch how fast the system landed 5,000 airplanes," he recalled. "It was within two hours that everybody was on the ground."

The center holds conference calls every two hours starting at 7 a.m. and ending at 9:15 p.m. On a recent morning, the 11:15 a.m. conference call came with more than 5,000 planes in the air and supervisor Paul Branch briefing around 100 participants, including representatives of all the major U.S. airlines and various air-traffic control centers.

He told listeners on the call of the 50-minute ground-delay program for most planes coming into San Francisco because of fog and said his center was monitoring potential storm systems in South Florida, New Mexico and Chicago.

To help address the problem of persistent delays, the FAA is trying to get NextGen off the ground, moving from ground-based radar to satellite-based tracking of planes. a much more advanced version of the GPS systems now present in most vehicles.

NextGen's advocates say the upgrade would reduce costs, minimize delays, increase capacity and reduce controller workloads. FAA Administrator Randy Babbitt recently said it "represents the next milestone in aviation innovation."

But the program is facing significant hurdles, as the airline industry is reluctant to spend billions of dollars to retrofit its planes with costly new technology without the assurance that the changes will be cost-effective.

"Frankly, for many airlines, it's expensive to upgrade the aircraft with this new technology, and until they know there's going to be a return on the investment, it's difficult to make that case," said Steve Lott, a spokesman for the Air Transport Association, a trade group.

Lott said the FAA should implement short-term fixes, such as redesigning routes to help free up the overcrowded airspace over New York.

Boyd said the agency's current efforts weren't enough to reduce flight delays significantly. He said that current flight patterns, in which planes are neatly lined up, as if along highways, as they fly to their destinations, were a key culprit.

"If we have congestion, it's because of those highways," Boyd said. "And all NextGen is going to do — and they admit this — is we'll be able to have more highways in the sky.

"That's the wrong approach. We're using around 4 percent of the sky now. We need to use all of it."

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