CHICAGO (AP) -- When Harvey ''Chip'' Reed has a few hours to kill between flights at Chicago's O'Hare International Airport, he doesn't wander aimlessly or fill up on fast food. He works out.
He is among airline passengers who squeeze in a little exercise during layovers or flight delays. It's getting easier for people like Reed to find fitness centers at airports, or near them, that welcome drop-ins. In Chicago, Reed heads straight for a health club at an adjoining hotel.
''It's just sanity when you're traveling,'' the 44-year-old said before beginning a workout during a recent four-hour layover on his way home to Truckee, Calif.
It was his second workout of the week at the Hilton club, which is connected to the airport through an underground passageway. He's even brought his family on vacation layovers; he and his wife work out while their two children go swimming.
''I don't understand why more airports aren't capitalizing on it,'' Reed said.
Graphic designer Kevin Gillotti also hates wasting time between flights when he travels for business or duathlon competitions _ running-biking-running events. A few years ago, he began looking for gyms around airports and now lists them on his Web site, www.airportgyms.com.
''I would spend a lot of time doing nothing in airports. I wondered how easy it would be to leave the airport and go work out,'' said Gillotti of Carlsbad, Calif.
His Web site now lists more than 50 health clubs in the United States and Canada. Most of the gyms are a short taxi ride away and cost $5 to $15. A few are in airports or airport hotels.
Gillotti said he gets updates and additions from other travelers.
''This is really for the fanatic that I admit that I am,'' he said.
Bill Dingell of Reston, Va., said he tried a layover workout en route to his honeymoon a couple years ago after coming across the Web site.
Dingell and his wife, Kara, hopped in a taxi at the Mexico City airport and used their membership at a Gold's Gym. His only disappointment was that the gym's T-shirts on sale were too small for him.
''They let us right in. They were glad to see us,'' Dingell said.
In Las Vegas, travelers don't even have to leave the airport to work up a sweat. Health club operator, 24 Hour Fitness, runs a center inside McCarran International Airport near baggage claim. Travelers can use it for a $10 fee. Spokeswoman Patricia Guinto said the club was opened four years ago for airport employees as well as passengers.
''For people on their layovers and people who are delayed, they're either bored or stressed ... working out relieves both of those things,'' she said.
Airport employees, pilots and flight attendants make up the bulk of the clientele at the Chicago airport Hilton, but there's a steady stream of passengers who hear about the club from other travelers, said manager Bob Smith.
''People who work out talk,'' Smith said.
American Eagle pilot Ken Thomas, who commutes from St. Louis to Chicago, said he comes in a little early to exercise before reporting to work.
''It's great to work out instead of sitting in a chair for a couple of hours,'' he said.
Mike Harrington, supervisor of the Hilton health club at Boston's Logan International Airport, said even passengers who don't have workout clothes with them can take advantage of the steam room or sauna, and they sell $12 disposable swimsuits for the pool. He said the club gets five to 10 visitors a day, and more during winter delays.
''You can go to the bar and have a beer and a hamburger or you can do exactly the opposite'' and exercise, he said.