Average air fares at the end of 2016 hit their lowest levels since 2009, according to the U.S. Bureau of Transportation Statistics.

Nationally, the average fares purchased were $347 in the fourth quarter, according to the federal data released Tuesday. That's down 6.1 percent from a year ago.

While average fares have declined, airlines collect revenue from more sources, such as baggage fees.

Low fuel costs, competition from ultra low-cost carriers, no-frills fares and other factors have also driven fares down.

But airlines including Delta are pushing to drive fares higher, particularly as fuel costs rise.

In Atlanta, the average air fare in the fourth quarter of 2016 was $339.43, also the lowest level since 2009. It was down 8 percent from a year ago.

The fares are for round-trips, except for when a one-way fare is purchased, in which case the one-way fare is counted. One-way fares made up 36 percent of the fares calculated for the quarter.

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Air fares have been falling, according to the U.S. Bureau of Transportation Statistics