WASHINGTON — For more than four hours, Doug Pinkham sat wedged in seat 19C of a Delta Air Lines jet as the plane inched its way through tarmac congestion caused by a winter storm that struck Atlanta's international airport on a recent night.

His cell phone and laptop batteries died, preventing him from doing any work. He finished a book, then a crossword puzzle. Mostly, though, Pinkham just stared at the seat in front of him or chatted with his wife. The plane finally left for Washington at 2:55 a.m. — 7 1/2 hours late. Pinkham walked exhausted through his front door in Oakton, Va., at 5:30 a.m. Feeling fatigued, he skipped work that day, missing out on important meetings and phone calls. He estimated that his unexpected day off cost his nonprofit organization several thousand dollars.

"It's not just the delay that kills you," said Pinkham, president of the nonprofit Public Affairs Council in Washington. "It's the lost productivity at work. It's the missed meetings. It's the fact I have to deal with losing sleep and going through that ordeal and the fact it took me a couple days to recover."

While declining on-time performance rates have drawn the most public attention, an analysis of government data reveals another staggering toll of late flights: lost time and money.

During the first 11 months of last year, 1.6 million passenger flights were at least 15 minutes late. The total delay time added up to 170 years — up steadily from 98 years lost on 1 million flights during all of 2003. The average delay of a late flight has grown from 49 to 56 minutes during that period, the data show.

With the U.S. economy stumbling, regulators and lawmakers are turning their focus to the economic toll of such delays. In a speech to the Aero Club of Washington on Tuesday, Transportation Secretary Mary Peters estimated that flight delays cost the U.S. economy $15 billion a year. In an interview, she said she thought that figure was probably low.

"It is incredible," Peters said. "It means a loss to our economy, a loss to our productivity; it also means a loss in quality of life."

Peters, who often takes commercial flights, said delays can affect productivity even for passengers taking on-time flights.

The transportation secretary recently hopped on a 7 a.m. flight to New York to attend a 10 a.m. meeting with Mayor Michael Bloomberg. She said she could have taken a later flight but worried it might be delayed. In this instance, her flight arrived on time — compelling the nation's top transportation official to mill about Gracie Mansion for an hour before she could see the mayor.

"It was absolutely not an efficient use of our time," she said. "There were lots of other things I could and should have been doing."

Fliers arriving at the nation's busiest airport, Atlanta's Hartsfield-Jackson International Airport, would probably agree. They endured the equivalent of 3,475 days of delay on late flights from January through November, according to an analysis of the latest data available from the Bureau of Transportation Statistics.

Passengers arriving at Chicago's O'Hare International Airport lost more time: 4,619 days. The average late flight landed at O'Hare 62 minutes behind schedule.

Air travelers arriving and departing from Washington's three major airports suffered 4,897 days of late flights. These delays cost the regional economy about $267 million, according to a rough analysis of flight data by Stephen Fuller, director of the Center for Regional Analysis at George Mason University.

Despite advances in technology that allow workers to use laptops and send e-mails from cell phones or other portable devices, Fuller said, the economic cost was probably greater than his estimate. Delay data only captures time lost to flights, not passengers.

For example, it does not tally the effect on fliers who miss connections and then spend hours at airports trying to get on increasingly crowded planes. There is no way to measure how long passengers wait in security lines or how early they must now get to airports. The data do not tabulate how long passengers must wait for luggage. They also do not account for the air traffic system's growing inefficiency; many airlines have increased scheduled flight times to compensate for snarls.

"You just have the tip of the iceberg here," Fuller said. "The cost of delays has mushroomed into the economy, hospitality industry, businesses in general. It is affecting how we work, the efficiency of the economy. These costs occur every year, and they are getting worse."

Transportation officials say they have taken steps to address delays. Among the measures is redesigning congested New York-area airspace and culling the number of flights allowed to land and depart from John F. Kennedy and Newark international airports. Regulators say congestion on New York tarmacs is a leading cause of delays that ripple across the country.

Government officials are working on long-term solutions, too, including the development of a satellite-based air traffic control system that should help increase capacity.

But the system is still years away from full deployment, and bills that would help fund the program appear to be stalled in Congress.