With a growing choice of fitness options springing up at the world’s busiest airports, staying healthy while traveling has never been easier.

“Travel can be stressful, so it makes a lot of sense for airports to provide these services.”

- Susie Ellis, chairman and CEO, Global Wellness Institute

Airlines, airports and nearby hotels know travelers can't help but sit around a lot, so they’re offering spa services, health clubs, yoga studios and pools where they can unwind, work out and relax.

“They’re everywhere,” said Susie Ellis, chairman and CEO of the Miami-based Global Wellness Institute. “The offerings are very robust in the U.S., and Europe is catching up.”

There’s a two-mile walking circuit with mountain and park views at Phoenix Sky Harbor International Airport. You can get a $15 day pass to Westin Hotel’s fitness center, with running routes and a heated pool, at Detroit Metropolitan Wayne County Airport. The Hilton O’Hare Hotel, connected to Terminal 2 at Chicago O’Hare Airport, has “day use” rooms that include Wi-Fi and access to the fitness center from 9 a.m. to 6 p.m., at $79 per day on weekends and $99 on weekdays. Access to just the fitness center costs $22.40.

Michael McGilligan, general manager of the Hilton O’Hare, said business executives and families take advantage of the rooms, which have soundproof windows and blackout drapes. “Give the people what they’re asking for,” he said.

While services like these have been available to business and first class travelers for years, airport and hotel facilities are now offering them to economy fliers – for as little as $15, or even for free. And as air travel increases, so does the number of people who are willing to pay for them. 

According to the 2014 Global Spa & Wellness Economy Monitor report, the trend appeals to “travelers who have layovers and are looking to mitigate some of the travel-related stress being inflicted on their minds and bodies.”

“Travel can be stressful, so it makes a lot of sense for airports to provide these services,” Ellis said. “It’s just really a natural that when people are traveling they would want to have the option to do something healthy.”

Overseas airports are joining the wellness movement, as well.

Singapore Changi Airport, ranked No. 1 for the third straight year in the World Airport Awards, has fitness and spa services, a music bar lounge and a Balinese-themed rooftop swimming pool. Passengers who stay at the Ambassador Transit Hotel can use the pool and Jacuzzi for free, while others pay $13.91.

Flying Club Gold members on Virgin Atlantic Airways can use its “clubhouses,” which include spa services, at New York’s John F. Kennedy Airport and London’s Heathrow and Gatwick airports.

And services in the Middle East are not as plentiful, but they’re “over the top” where they exist, Ellis said.

Etihad Airways lounges at Abu Dhabi International Airport are open to first and business class passengers, and Six Senses spas are located in lounges in Terminals 1 & 3. Travelers booked in Etihad Premium cabins can book treatments at the spa reception on the day they travel.

Passengers at the Abu Dhabi airport can also unwind at TOSA Spa in Terminal 1, where express beauty services are available, and they can get traditional skin and body treatments at a second spa in Skypark Plaza, opposite Terminal 3.

But the largest numbers of fitness amenities can be found in American airports.

“The majority of the airports provided free access to rooms or areas within their terminals where passengers could squeeze in some low-impact walking, stretching or biking,” said Orbitz.com blogger Betsy Mikel. And many airport hotel fitness centers sell day passes “so passengers who wanted a more intense workout could hop on a treadmill, lift weights or swim laps,” she said.

Here are some of Orbitz.com’s “healthiest” U.S. airports:

San Francisco International Airport: Check out one of its quiet yoga rooms. Just be sure to leave your shoes, cellphones and conversation outside. Free mats and yoga equipment are available.

Philadelphia International Airport: Last year, the airport partnered with Smooth Fitness, a local gym, to install stationary bikes throughout the terminals. The light workout is free.

Dallas/Fort Worth International Airport: Try the free LiveWell walking path – 1,269 steps or .6 miles one way – and check out the 12 mosaic floor tiles, which are part of the airport's art program. 

Burlington International Airport: There’s a yoga and meditation space on the second floor that’s sponsored by Evolution Yoga, a local studio.

Detroit Metropolitan Wayne County Airport:  In addition to the $15 day pass to its fitness center, the Westin has mapped running routes around the hotel.