The volunteers of the Armed Forces Service Center call themselves Minnesota's best-kept secret.

Born during the Vietnam era when returning soldiers were sometimes scorned by a public soured by war, the group that welcomes traveling troops coming through the Minneapolis-St. Paul airport now struggles with a post- 9/11 problem -- a concern over security that means many people don't know of its existence.

The center's volunteers rely on donations from local businesses, nonprofits, and veterans' organizations for toiletries, muffins, coffee and other amenities to give troops in transit.

The group has greeted 171 military flights over the past three years. Last month, 3,000 troops passed through, drinking 35 pounds worth of Caribou Coffee and grabbing cell phones lent courtesy of Sprint. The Girl Scouts have been especially generous: a storage room has a well-stocked supply of Do-Si-Dos.

With the country at war on two fronts, the number of troops filtering through the airport has exploded, and the volunteers have found themselves knocking on more doors for donations.

The demand comes as the public's patience with the wars is being tested amid economic hardship. It also comes as the Twin Cities airport continues to operate at a high level of concern over security. The Twin Cities is the venue, after all, where convicted terrorist Zacarias Moussaoui was first arrested.

Debra Cain, the center's director, often gets advance word of incoming flights. But troop movements, and where they are coming from and going to, are treated as an issue of operational security. A soldier recently discovered he was going to be traveling through the airport on a layover and sent out e-mails about the schedule. In response, the military re-routed the flight.

"We try to work closely with the airlines and with the military," she said. "There's a lot of concern about keeping troop movement secure. At the same time, we're seeing more and more people coming through. We need funds, funds, funds."

Pat Hogan, a spokesman for the Metropolitan Airports Commission, which runs the airport, said Transportation Safety Administration regulations apply to airports across the country and that MSP has no history of being more restrictive. The airports commission donates space to the center but is not otherwise affiliated with it.

"The troops are required to be contained in a certain area; they're carrying guns and there is no screening process in terms of when they get off the plane and what they may have," Hogan said. "There are some security concerns that have to be taken into account."

Even with their new blue denim shirts with the letters AFSC embroidered on them (donated in 2008 by Kraus Anderson Construction), local volunteers might be forgiven if they have felt a little left out. Similar groups elsewhere seem to enjoy a much easier time and have flown far less under the radar.

The Maine Troop Greeters, for instance, have welcomed 841,000 troops since 2003 at the Bangor International Airport and have been the subjects of a multitude of attention, including face time with Vice President Joe Biden in the White House and players in a documentary film, "The Way We Get By," being screened this month.

The local center, which is not affiliated with the USO, was founded in 1970 by a woman whose son died in Vietnam. It has never closed.

Besides greeting flights at the gate with a mobile canteen of treats, the Armed Forces Service Center operates a center on the mezzanine of the Lindbergh Terminal. It has a large lounge with satellite TV, free Wi-Fi, complimentary sandwiches, pastries, cereals and soups and bunks for men and women. In the days after 9/11, 16 Marines were stranded there for five days while commercial flights were grounded.

Teacher Jeanne Morford volunteered for the first shift and has returned for a four-hour stint every Monday. Like many of the volunteers, Morford became involved in the center after seeing how troops returning from Vietnam were being treated.

"We should never treat people who have served their country like that again," said Morford, the one-time president of the group. Another volunteer, Annie Olson, began writing letters to soldiers in Vietnam in 1968 and has volunteered at the center since 2004.

"I feel it's the best way I can give back to people who have sacrificed so much," she said.

Don Wille, whose stepson Chris is in the Army, learned about the center when his wife, Renee, became involved in a military family support group. He ended up delivering several truckloads of snacks and personal hygiene items donated to his business after learning of the critical need for supplies.

"It's either the first place when they get to American soil or the last place before they leave," he said. "They need to have a good reception one way or the other because they are going to be gone for a long time or they've been gone for a long time."

While soldiers are being given more support than during the Vietnam days, a recent flight in by a group of Marines provided a glimpse of some of the new problems in dealing with weary troops facing extended deployments.

Two and a half hours late after their flight had mechanical difficulties, the Marines filtered through, some staring with fatigue, others happy to have a conversation with the volunteers. Two Airport Police officers monitored movements the whole time.

As the Marines marched on to their next flight back to their base in Arizona, volunteers from the center made a point of going through the restrooms to make sure no one was planning to go AWOL. It has happened before.

But not on this date. All troops were accounted for and within 45 minutes after the plane landed, the volunteers were breaking down their mobile canteen like a NASCAR crew at a pit stop. Their effort did not go unnoticed.

"After six or seven months of a long deployment you kind of forget that there are people here supporting you," said Staff Sgt. Nicholas Cook, whose unit, Marine Wing Support Squadron 371, was returning to its home base in Yuma, Ariz. "When you jump off the plane and see something like this, I am taken aback. It can't help but put a smile on your face for the rest of the trip back home."

It was the end of Cook's third deployment. "Back and forth, this is my sixth time seeing something like this," he said, "and I never get used to it."

Mark Brunswick • 651-222-1636