Southwest Airlines Co. said Monday that traffic rose 8.6 percent in December, leaving fewer empty middle seats.
The average flight was 83 percent full last month, compared with 82.7 percent in December 2014.
Dallas-based Southwest said it continues to expect that a key figure -- revenue for every seat flown one mile -- was flat to down 1 percent in the fourth quarter. That suggests average fares were lower than in late 2014.
Virgin America Inc., based in Burlingame, California, said that its December traffic rose 3.6 percent but occupancy slipped to 82.2 percent from 82.3 percent a year earlier.
Last week, Delta Air Lines Inc. reported that December traffic rose 1.6 percent and the average flight was 84.4 percent full, up from 83.7 percent the previous December. The revenue per seat figure fell 5 percent, with most of the drop attributed to currency-exchange rates and more Thanksgiving travel pushed into November.
In midday trading Monday, Southwest shares were down 26 cents to $41.95; Virgin America shares fell 71 cents to $32.16.