Southwest traffic rises 11.3 percent in December

DALLAS — Southwest Airlines Co. said Friday its traffic rose 11.3 percent in December, compared to the final month of 2009, as it added more seats and if flew fuller flights.

The Dallas-based airline said it flew paying passengers 6.6 billion miles last month, compared to 6 billion in December 2009. Its capacity, or available seat miles climbed 5.6 percent to 8.3 billion. An available seat mile measures one seat flown one mile.

The airline's load factor, or occupancy rate, was 80.4 percent compared to 76.2 percent for the same period last year. It also said passenger revenue per available seat mile — a key measure of airline performance — is estimated to have increased about 5 percent compared to December 2009.

For the fourth quarter, Southwest flew paying passengers 20 billion miles, up 10.1 percent from 2009. For 2010, it flew paying passengers 78 billion miles, up nearly 5 percent.

Southwest shares climbed 18 cents to $13.34 in afternoon trading, while broader indexes declined.