Southwest Airlines Co. warned that costs will climb faster than expected as it grapples with heavy labor expenses, undercutting gains from strong demand for leisure travel.Non-fuel unit costs will rise as much as 9% in the first quarter after an 11% jump in the final months of last year,

U.S. budget carrier Southwest Airlines' fourth-quarter profit surpassed Wall Street estimates on Thursday, helped by robust travel demand and improved airfares. The airline also forecast better-than-expected unit revenue (RASM),

Southwest Airlines (LVU) put in a solid performance in the fourth quarter and forecast above-consensus revenue per available seat mile for the current quarter as the carrier absorbed surplus capacity across the industry with greater aircraft efficiency and higher airfares.