The Department of Transportation has released its report detailing airline-related consumer complaints for the 2013 calendar year. According to the report, complaints were down 14.1 percent from 2012. Since the report includes only complaints from consumers who have taken the extra step of contacting the Department of Transportation, it is somewhat limited in scope.

The Department received 13,168 complaints in 2013, down from the 15,338 complaints filed in 2012. Complaints about frequent flyer programs were also down from 289 in 2012 to 254 complaints in 2013.

It was no surprise that Southwest topped the chart with the fewest complaints. Frontier, in the process of transitioning to an ultra-low-cost business model, came in at the bottom with the highest level of complaints. Alaska Airlines, Delta, JetBlue and AirTran rounded out the top five carriers with the lowest level of complaints. American and United joined Frontier at the bottom.