GRAPEVINE, Texas — A few times each month, Karen Marks stands among the volunteers greeting the troops who land daily at Dallas-Fort Worth International Airport, all on two weeks' leave from Iraq or Afghanistan.

One recent day was different for her. Somewhere among the few hundred troops was Marks' son, a 20-year-old Marine lance corporal named Michael.

"You're over here worrying about the unknown ... (and) when you finally get to see them again, all the love from when you gave birth just comes right back into your heart," Marks said between sobs of joy.

Even after their own family's reunion, Marks and husband David remained at their post inside the airport's Terminal D until the very last service member had walked through the sliding glass doors, hugging and shouting greetings to the troops.

"I've seen kids ask for their autographs because these are their heroes," Marks said. "I know they're tired and they're overwhelmed, but it's just so good for them to know that we care and we love them. For my own son, my heart was going to explode."

Every day at DFW and Hartsfield-Jackson Atlanta International Airport, troops land on their way home for leave from overseas deployments, and every day they're greeted by flag-waving, appreciation-shouting crowds of volunteers from a program that's called Welcome Home a Hero in Dallas DFW and USO Operation R&R in Atlanta.

A similar group, the Maine Troop Greeters, has met more than 500,000 service members since 2003 as they passed through Bangor International Airport, where planes carrying troops often stop to clear customs, refuel and change crews for continuing flights.

At the Atlanta airport, USO volunteers man a welcome booth most days and lead the applause for arriving troops. They gather troops who are ready to check in for departing flights overseas and march them through the airport's main atrium before cheering crowds.

Heading the line of cheerleaders in Dallas is Donna Cranston, 50, of Coppell, the volunteer coordinator. She missed the program's first day in June 2004, but she's been at the airport most days since.

"What I think I learned early on is it doesn't matter how routine it is for us. For these guys, it's their first day back on American soil in months, and they need to know they're supported and they're loved and appreciated," Cranston said. "And it's one of those things that you never grow tired of."

Every day, the military calls Cranston with the troops' arrival times, the same information they post on a hot line for the public. She arrives with small, stapled pieces of paper listing the next flight times, airlines and terminals for major cities.

"What terminal do you need, soldier?" she said recently as the troops dashed by her.

"First bus on the left," she directed another.

"International or domestic call?" Cranston asked a third service man, tossing her cell phone to him.

One of the program's goals "is to allow people to show their support," Cranston said. "But our main goal is to get the troops through the line and get them to their flights so they can get home to their loved ones."

Inside Terminal D, the arriving troops walk through a glass-enclosed catwalk, visible to waiting passengers, before going through customs and picking up their luggage. Every day, there are a few greeters on the floor below the catwalk, cheering and screaming for the troops, who often smile, wave and take photos of their supporters.

Other passengers often applaud, too, standing up as they realize what's happening.

Since the R&R program began, about 224,000 troops have arrived at the airport from duty overseas, while 217,000 others have departed on their way back to the Middle East.

"It opens up a whole new perspective of life, being over there and having everything taken away from you, coming back, seeing loved ones," said Michael Marks. "It's a really great moment for me."