Southwest Airlines will cut routes from Philadelphia to four U.S. cities in January and will scale back on flights to Boston in February.

The affected routes, Pittsburgh, Jacksonville in Florida, Manchester in New Hampshire and Providence in Rhode Island, are the first cuts for the nation's largest low-fare carrier this year, according to Southwest spokesperson Ashley Dillon.

"Keeping in mind that we need to be profitable on all the routes that we fly, with the cost of fuel rising we just have to make decisions on specific routes," Dillon told Reuters on Wednesday.

"There are a couple routes in Philadelphia where we discontinued the nonstop service ... and those routes we have stopped, we don't see those coming back for the foreseeable future."

Dillon said it is common for Southwest to adjust schedules to consumer demand, but the move in Philadelphia is unique to those specific markets where the competitive environment is affecting profitability.

Southwest will cut over 100 flights by January, but will add back 120 by February for a total of 3,200 flights - though not the Philadelphia retired routes.

The Dallas-based Southwest recently acquired AirTran Airways and serves 72 cities in 37 states.