Something was missing at Washington Dulles International Airport, realized customer service manager Dennis Hazell. For grown-ups, the concourses offered sports bars and duty-free shops. For dogs, "pet relief areas" beckoned with fake fire hydrants on artificial grass. But for the youngest travelers, there was zilch, nothing.

"We had forgotten a huge part of our customer base," says Hazell, who saw kids getting out their preflight wiggles by crawling beneath seats and leaping over luggage.

That changed with the arrival of the FunWay, an indoor play area sponsored by NASA that turns three years old in August. Thousands of visitors have hung out by gate B70 to scramble over its squishy foam airplanes and the smiling "Tommy Tower," a control tower with a few improvements. "There are steps on one side, a slide on the other, and you can crawl through an opening underneath Tommy," Hazell says.

Parents have long seen the need for kid-friendly spaces like these, and they're finally taking off, according to Jeff Williamson, business development director for Playtime, the Denver company behind the Dulles FunWay. In the past 15 years, Playtime has installed more than 50 airport play areas in cities around the world, including Beijing, China, and Calgary, Canada.

Chances are, the Tovmasyan family has spent time at many of them.

"We travel a lot - more than we want to," Mari Tovmasyan says.

Her husband Hayk's job with the U.S. Army means they've bounced around the world with their two sons, ages 3 and 5. For now, they're based in Vicenza, Italy. They're always on the lookout for ways to stay entertained, whether it's a piano player at the Brussels Airport (in Belgium) or the taxidermy animals on display at the airport in Anchorage, Alaska.

That's why Mari Tovmasyan always researches kid stuff at each airport along the way whenever they book a trip.

"Connecting flights are the most important," she says, noting that recent hits have included the play areas at Baltimore-Washington International Marshall and Warsaw Chopin in Poland.

Knowing that families often select flights based on these offerings, some airports are going above and beyond. Take, for example, Germany's Munich Airport, located next to a visitors park with a playground, mini golf and vintage aircraft to explore. Each November, a winter market pops up between its two terminals.

"Kids love ice skating; parents love the gluhwein," notes Philipp Ahrens, the airport's head of center management. (Gluhwein is a mulled wine drink popular in Germany at Christmastime.)

But the big draw for families, Ahrens says, is Kinderland, a dropoff day-care facility for ages 3 to 10. Kids can jump in a ball pit, build at a Lego station, make crafts or get a glitter tattoo.

The world's most kid-friendly airport? It's probably Changi in Singapore, where you can spend a layover wandering at a butterfly garden, creating a woodblock print, feeding koi fish, or climbing around Chandelier, a five-story red net structure. On April 17, the airport will open a new building with a 130-foot indoor waterfall, giant trampolines, hedge mazes and "foggy bowls," where puffs of mist are meant to make it seem as if you're playing in the clouds.

For most airports, these kinds of projects are too expensive and take up too much space.

But expect to see more innovation in play areas, Williamson says. For example, an upcoming Playtime project for Charlotte Douglas International in North Carolina will include a bench with built-in lights that react to touch. He also predicts more "vertical play" (translation: climbing!), as well as charging ports to power up devices.

At Dulles, Hazell hopes to get the money to install two more play areas, possibly featuring interactive touch screens. "It's on our wish list," says Hazell, who hopes to have at least one added by the end of the year, just in time for family winter vacations.