Airfares from Denver to destinations within the United States rose by 8.4 percent in the first quarter compared with a year earlier - double the average increase nationally, according to the latest federal data.

And there's not much relief in sight: Leisure and business fares across the country this summer are up about 10 percent, some experts say, and likely will continue to rise as airlines cut flights this fall. Those reductions, which are largely tied to steep increases in fuel costs, will allow airlines to raise prices even further because there's less supply in the market.

"Normally, fares drop off in the fall, but with the capacity reductions coming up you're going to start to see off-season fares that are comparable to the summer," said Bob Harrell of New York-based airline consultancy Harrell Associates. "The sky is the limit" for increases at this point.

The average domestic fare at Denver International Airport ballooned to $324.89 during the first three months of the year, about $30 higher than the same period in 2007, according to the Bureau of Transportation Statistics. The numbers include round-trip tickets and one-way itineraries that don't include a return flight.

Nationally, domestic fares increased by an average of 4.4 percent, or nearly $14, to hit their highest levels since the second quarter of 2006.

Local travelers still have it pretty good, though, as fares from DIA in the quarter came in slightly below the $331.72 national average.

Denver has benefited from new low-cost service in recent years that pushed down fares significantly, even as prices rose across the U.S. Fares at DIA now appear to be playing catch-up as both United Airlines and Frontier Airlines eliminate flights.

Still, Southwest Airlines could help keep fares in check. The carrier, which typically offers steep discounts when it starts new routes, is more than doubling it presence in Denver this year.

Fares in 17 other cities also increased at a higher rate than Denver's average during the first quarter. Boston posted a 15.6 percent spike, while ticket prices at Dulles International Airport in the Washington, D.C.-area jumped 15.2 percent.

Cincinnati had the highest overall domestic fares in the nation - at $535.32 - while Atlantic City, N.J., had the lowest - at $108.71 - among the 100 airports included in the report. Atlantic City, which has a tiny airport with few commercial flights, also posted the largest decline in airfares with a whopping 48.6 percent dip.

walshc@RockyMountain News.com or 303-954-2744

Rising prices

Airports and their average airfare increases in the first quarter compared with a year earlier (and average fare in the first quarter*) 1. Boston: 15.6 percent ($387.56)

2. Washington Dulles: 15.2 percent ($417.65)

3. Houston Bush: 14.5 percent ($404.70)

4. Washington Reagan: 13.7 percent ($396.94)

5. Chicago Midway: 13.3 percent ($253)

19. Denver : 8.4 percent ($324.89)

Average: 4.4 percent ($331.72)