It’s hardly in the Southwest, but Philadelphia recently became a new stop for Southwest Airlines, much to the chagrin of US Airways, which has dominated traffic at the airport for years.

Southwest currently operates 14 flights a day to six cities from Philadelphia, and will add another 14 flights and seven destinations on July 6. US Airways has 392 daily flights. The airport expects Southwest will add about 1.3 million new passengers to its nearly 25 million annual passengers.

Both carriers have been engaged in a blitz of public relations and marketing efforts. US Airways recently engaged in what the company calls a campaign of “unbelievable acts of kindness, ” involving everything from putting money in people’s parking meters to filling gas tanks to providing free cheese steaks. Southwest’s founder Herbert Kelleher paraded along the Terminal E skybridge with airport director Charles Isdell as a traditional Philadelphia Mummers band played “Happy Days Are Here Again.”

US Airways has even slashed fares out of Philadelphia, with one-way fares to Boston’s Logan Airport selling for as low as $44 in coach and $299 in first-class. In a further attempt keep the low-fare competitor at bay, US Airways is offering double and triple miles for flights between Philadelphia and Birmingham, Ala., Chicago, Fort Lauderdale, Fla., Houston, Indianapolis, Kansas City, Mo., Little Rock, Ark., Los Angeles, Manchester, N.H., Nashville, Tenn., New Orleans, Orlando, Fla., Phoenix, Providence, R.I., Raleigh/Durham, N.C., San Diego, Seattle, St. Louis, Tampa, Fla. and West Palm Beach, Fla.

Through Sept. 1, all those flights will earn double miles; if they’re booked online, they’ll earn triple miles.

“Southwest’s arrival here really raises the bar for US Airways,” T. Jeffrey Shull, chief of staff for Philadelphia International told The Boston Globe. “It’s kind of a make-or-break proposition for them.”