The Indianapolis-based carrier said its scheduled service passenger load factor increased 3.3 points, to 79.1 percent, compared with December 2005.
Scheduled service traffic was down 15.4 percent and total passengers fell 32 percent, to 217,029, in December.
But comparisons are difficult because ATA slashed service and aircraft last year as part of its bankruptcy reorganization, which has been completed. As part of the reorganization, ATA last year eliminated all scheduled service at Indianapolis International Airport, where it was the busiest carrier for several years.
ATA now focuses heavily on routes from Chicago to the East Coast and from the West Coast to Hawaii, through a code-sharing agreement with Dallas-based Southwest Airlines.
Meanwhile, ATA has been trying to grow its air charter service, which consists mainly of ferrying U.S. troops and government personnel.