The Transportation Security Administration is reminding airport travelers that it's fine to stuff carry-on bags with clothes and toiletries. Just don't pack any heat.

TSA announced that its officers seized 4,432 guns at checkpoints last year — the most in the agency's 18-year history. It says that 87% of those guns (some 3,855) were loaded.

"The continued increase in the number of firearms that travelers bring to airport checkpoints is deeply troubling," TSA Administrator David Pekoske said in a statement Wednesday.

He points out that it isn't illegal to bring firearms to the airport, but that there are well-established rules people need to follow when traveling with guns.

"There is a proper way to travel safely with a firearm. First and foremost, it should be unloaded," Pekoske said. "Then it should be packed in a hard-sided locked case, taken to the airline check-in counter to be declared, and checked."

Nationwide, TSA says it caught firearms at 278 airports. That includes, as NPR reported in July, a missile launcher found in a Texas man's luggage at the Baltimore/Washington International Thurgood Marshall Airport.

Travelers at Hartsfield-Jackson Atlanta International Airport had the most guns seized: 323 firearms. That's about 100 more firearms than at the next closest airport.

That would be Dallas/Fort Worth International, with 217. Denver International came in with 140, George Bush Intercontinental in the Houston area had 138, and Phoenix Sky Harbor International had 132, according to TSA.

TSA's guidelines for transporting firearms and ammunition says items such as firearm magazines, clips and firing pins are banned from travelers' carry-on luggage but can be put in checked baggage.

Firearm replicas, including toys or other gun-shaped items, also must be transported in checked luggage.

Something that is permitted in carry-on luggage: rifle scopes.

The TSA report released Wednesday says the number of firearms caught at checkpoints last year averages out to about 12 per day.

In fact, the number of firearms found at TSA checkpoints has increased every year since 2009, when officers confiscated 976 guns.

TSA spokesperson Lisa Farbstein tweeted Thursday that officers at Newark Liberty International Airport already "caught the first gun of the year at a checkpoint yesterday, just two weeks into the year."

She adds: "Man was arrested by the police. Last year, TSA caught 11 handguns at the airport's checkpoints."

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