PHILADELPHIA - Southwest Airlines said Thursday that it will double the number of flights it operates in and out of Philadelphia, raising the competitive stakes with US Airways, the dominant carrier in the city.

Just weeks before Southwest moves into Philadelphia, hitting struggling US Airways with low-fare competition, colorful Southwest Chairman Herb Kelleher swooped into town for a bus tour with reporters.

Kelleher announced that after starting May 9 with 14 daily flights, Southwest will quickly expand service on July 6, adding trips to the Boston area and other cities and increasing flights to 28.

But Kelleher discounted fears voiced by David N. Siegel, president and chief executive officer of US Airways, that Southwest posed a major threat to that airline's future.

"He's trying to win concessions from his employees," Kelleher said of Siegel.

Siegel had said in a video conference with employees a day earlier that US Airways' survival was at risk without major concessions from labor groups.

"Herb Kelleher wants your job," Siegel said. He said matching Southwest on fares would require severe cost-cutting that would mean labor groups could face pay cuts as high as 25 percent.

US Airways has lost when it has gone head-to-head with Southwest in Baltimore and on the West Coast, Siegel said, predicting that if his airline couldn't hold its position of strength in Philadelphia, "they're going to kill us."

"Baltimore is not Philadelphia," Kelleher said. "Baltimore was never the size of Philadelphia for US Airways.

"We will have 28 flights as of July 6. US

Airways must have, what, 400 a day?" Kelleher said. "This is not the Viking killer ship coming in."

The Philadelphia area is getting a reintroduction to the flamboyant low-fare entrepreneur, who grew up in neighboring Haddon Heights, N.J., but has returned only occasionally since he moved to Texas in 1960, "permanently."

Like a campaigning politician, Kelleher rode the bus to Haddon Heights High, where he graduated in the Class of 1949. He was presented with a photo collage and a school banner, to shouts of "Way to go, Herb." He signed copies of the Garneteer yearbook for former neighbors and admirers.

Back in Philadelphia, he ate local food, emulating the likes of Democratic presidential candidate John Kerry, who picked at a cheese steak at Pat's King of Steaks, and former mayor and now Pennsylvania Gov. Ed Rendell, who wolfs hoagies at campaign stops and other opportunities.

Scott Franks, chief executive officer of Tierney Communications, a Philadelphia public relations and advertising firm, said Kelleher indeed can resemble a campaigning politician, only "more fun."

"I have fun at everything I do," Kelleher said. "The alternative is rather dreadful, I think."

Michael Useem, a management professor at the University of Pennsylvania's Wharton School, said that unlike chief executives who stay for a few years, Kelleher co-founded Southwest and is solidly identified with the airline.

"It makes him a folk hero in sense of (the late Wal-Mart founder) Sam Walton," he said.