Sea-Tac Airport, which set new passenger traffic records for the past two years, saw traffic decline in September.

Passengers numbers in September declined by .45 percent, a dip of 12,678 passengers to 2,830,493 compared with September 2011.

For the year, however, the airport passenger statistics show a growth of 1.49 percent, a increase of 371,137 over the first nine months of last year.

Sea-Tac’s traffic volume increases mirrored airports nationwide which showed only minor increases for the year through September.

Dallas-Fort Worth International Airport, for instance, reported an increase of just 1.2 percent through September.

Chicago’s O’Hare Airport showed a more robust increase through the first nine months, 3.89 percent.

Alaska Airlines and its sister airline, Horizon Air, which flies under Alaska’s brand, remained the airport’s dominant carrier with 49.98 percent of the passenger traffic including trips flown by SkyWest for Alaska through September.