In addition to firearms, TSA agents uncovered a number of hand grenades, a lipstick knife, and a sword cane.

Credit: Photo by Joe Raedle/Getty Images

The Transportation Security Administration (TSA) discovered a record-breaking number of firearms inside carry-on luggage in 2017: 3,957.

About 84 percent — or 3,324 of those weapons — were loaded, according to the TSA's annual report.

The number of firearms was up from 2016's record of 2,815 loaded firearms and 3,391 overall, accounting for a 16-percent increase year-over-year.

The increase since 2005, the first year included in TSA's 2017 report, is even starker. TSA agents have found that the number of firearms being discovered in carry-on luggage has been multiplied six times over, with just 660 firearms uncovered in 2005.

During that same period, gun ownership in the U.S. has dramatically decreased, according to a variety of polls conducted by Gallup, the General Social Survey, and others. One CBS poll in 2016 reported that gun ownership was at a 40-year low.

While fewer people are buying guns, people who do buy them are buying more than they ever have, according to statistical data. The average gun owner in the U.S. now possesses eight firearms, with half of the guns in the U.S. belonging to just three percent of the population, according to a recent Harvard and Northeastern University study obtained by the Guardian.

TSA's screening technology has seen major advances in the years following 9/11, and the higher rate of firearm discovery might be tied more closely to better screening systems than to a jump in the number of people attempting to bring firearms through airport security.

Passengers are allowed to travel domestically with their firearm on most flights as long as they pack it, unloaded, in their checked luggage and not their carry-on. The TSA requires passengers to declare any firearms in their luggage when checking bags.

The top airport for firearm discoveries in the U.S. was Hartsfield-Jackson Atlanta International Airport, with 245 firearms. Dallas/Fort Worth International landed in second place.

In addition to firearms, TSA agents uncovered a number of hand grenades, a lipstick knife, and a sword cane.