Seniority issues with the hundreds of incoming AirTran flight attendants already have been worked out, with Southwest flight attendants getting an extra 21/2 years of seniority over their AirTran counterparts, Stone said. But tensions remain as AirTran flight attendants transition to Southwest hubs.

About 2,200 AirTran flight attendants were in a separate union at the time of the acquisition, Stone said. Between 500 and 600 will have transitioned to Southwest by the end of this year, she said.

Many of AirTran's most veteran flight attendants, who are transitioning to Southwest first, have requested to be stationed out of BWI because it is one of the closest Southwest hubs to Atlanta, where AirTran was based, Stone said.

"Baltimore has seen a shift in flying seniority, more so than other bases with the acquisition," she said.

Seniority is a major issue for flight attendants, because it is a key determinant in how they get to select routes, hubs and schedules.

As Stone and other union representatives negotiate their new contract, they will likely keep job security under the acquisition at the forefront of their minds, said Lee Hays, a former aviation contract negotiator and an assistant professor who teaches aviation labor relations at Embry-Riddle Aeronautical University.

Amid such transitions — and the "continuing shake-out in the aviation industry, in which the major players, what we call the legacy carriers, are simply looking to expand their routes and grow" — there come a "lot of labor issues," Hays said.

As companies like Southwest are watching their bottom lines, unions are keen on maintaining "past practices" that benefited them and avoiding new policies that could chip away at the protections they have won over the years, he said.

"If I were a flight attendant at Southwest, I would be saying, 'As they bring these [AirTran flight attendants] in, we'd love to have them, as long as they aren't replacing us,' " Hays said.

According to Michael Boyd, president of the aviation consulting firm Boyd Group International, the idea that Southwest might lose touch with its positive labor stance amid the transition is "a legitimate fear" to have as the company grows.

"As you get bigger, lines of communication get stressed," he said. "With the AirTran transition, there is always going to be a little bit of heartburn."

Still, Boyd said he doesn't expect too much trouble at the negotiating table after decades of labor peace at Southwest.

Stone said she's ready for the back and forth that inevitably comes with high-stakes negotiations.

She is younger than her predecessors and is the first woman to be the local's president in 13 years, despite the union membership being about 80 percent women. But that, she said, has only translated into more support from the union's membership.

Back in 2004, Stone was working in public health when she decided to become a flight attendant and travel for a few years. She thought it would be an adventure before going to graduate school.

Once at Southwest, however, she felt she had become part of a family, she said.

"We have always been given the freedom to be more ourselves on the planes, to joke with customers," she said.

It's that culture she wants to protect in whatever contract she signs off on, she said.

As for her own future, Stone said she'll see what happens when her term as union president ends in 2015.

"I could be here another 20 years and still not have found all the charm Baltimore has to offer," she said.