Southwest Airlines Co. (LUV) on Wednesday said it now expects fourth-quarter available seat miles to increase by about 21%, compared to its earlier view of no change. Its outlook for fourth-quarter revenue seat miles improved to a drop of up to 10% from its earlier view of down as much as 11%, as “travel demand and yields continue to be healthy.” The carrier said leisure demand “remains strong” on the heels of Thanksgiving holiday revenue. “Close-in bookings, including managed business bookings, have performed at the better end of expectations in November and December-to-date,” Southwest said. Southwest said it now expects fourth-quarter unit revenue to improve to the better end of its previous guidance range, and it continues to expect record fourth-quarter operating revenues and record fourth-quarter passengers. On the minus side, economic fuel costs per gallon for the fourth quarter are expected to be $3 to $3.10, up from its earlier estimate of $2.90 to $3.