Complaints filed by air travelers about commercial airlines dropped by 14% in 2013, compared to the previous year, according to federal statistics released Tuesday.

During last year, airline passengers filed 13,168 complaints with the U.S. Department of Transportation, down from the 15,338 complaints filed in 2012, according to the federal agency.

The decline came despite a drop in the overall on-time performance by the nation's largest carriers. In 2013, the carriers reported a 78% on-time arrival rate, down from 82% in 2012, according to federal data.

For all of last year, the carriers also lost, damaged or mishandled luggage at a rate of 3.22 bags per 1,000 passengers, up from the 2012 rate of 3.09.

The nation's airlines do not disclose complaints filed directly with them, and passenger rights advocates say those complaints likely far outnumber those submitted to the government.

In the month of December, the country's largest airlines reported 10 incidents in which domestic flights were delayed on a tarmac for more than three hours and four international flights that were delayed more than four hours. Most of the reported tarmac delays involved United Airlines flights that were grounded at Chicago O’Hare Airport during a snowstorm on Dec. 8.  All of the reported delays are under investigation by the U.S. Department of Transportation.

In 2010 and 2011, the federal agency adopted rules giving it the power to impose fines against airlines of up to $27,500 per passenger for such delays.

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