One Monday last month, a 41-year-old Somerville woman was stopped at a Logan International Airport security checkpoint by agents who discovered a prohibited item in her carry-on bag.
It wasn’t the usual sort of thing — an extra-large water bottle, a forgotten shampoo container, or even a pair of scissors. It was a gun: a Smith & Wesson .380 caliber handgun with a bullet in the chamber.
As astonishing as it may seem in an era of heightened security and terrorism threats, the number of air travelers caught with guns in their carry-on bags has increased in recent years.
The number of passengers who tried to bring guns onto planes in their carry-on bags jumped from 976 in 2009 to 1,813 in the United States last year, according to the Transportation Security Administration. The number of incidents climbed 16 percent in 2013, compared with the prior year, and confiscations are up again this year.
Eighty-four percent of the guns found last year were loaded, according to a Northwestern University analysis.
The TSA says most people claim they simply forgot they were carrying a gun.
“How does that happen?” asked David Borer, general counsel for the American Federation of Government Employees, the union that represents more than 45,000 TSA workers. “They don’t forget to put on their pants. They don’t forget to bring a toothbrush. But oh hey, they forgot they brought a gun? They’ve been on notice for this for 10 years, and it’s time to grow up and be responsible.”
The rate of gun detections at Logan is below the national average and is the fifth-lowest for all US airports with incidents last year, according to a Globe analysis of TSA and Federal Aviation Administration data. Guns were discovered on just six travelers out of a total of 14.7 million who departed from Logan last year. There have been five incidents at Logan so far in 2014.
Only John F. Kennedy International and LaGuardia Airport in New York, Newark Liberty in New Jersey, and Mineta San Jose International Airport in California had fewer cases per traveler. The highest was at Raleigh County Memorial Airport in West Virginia.
These type of incidents are one reason why the TSA enforces such tight security screening procedures, which travelers often find cumbersome.
“We have to be careful that people do not carry weapons through or try to carry weapons through,” said Ed Freni, director of aviation for the Massachusetts Port Authority.
Guns aren’t the only weapons confiscated by TSA agents. In a weekly blog distributed by the agency, they have reported finding inert grenades, knives, stun guns, brass knuckles, spear guns, and a samurai sword.
“More than a dozen years after 9/11, you’d think people’s awareness would be raised,” said Lisa Farbstein, a TSA spokeswoman. “But they continue to bring firearms and weapons to checkpoints every day. The numbers just keep going up.”
Farbstein said weapons at checkpoints cause delays and slow the screening process for other travelers because law enforcement must respond to each incident.
Some security experts and gun policy specialists point to loose gun laws and a lack of enforcement in some states as reasons why more travelers bring guns to airports. Guns in carry-on bags appear to be more common at airports in rural areas and in the South, where gun laws are generally more relaxed, according to TSA data.
While it is against the law to carry a gun on a plane, stiff charges don’t always follow the discovery of a firearm.
The TSA can impose heavy civil penalties, up to $11,000, against gun-toting travelers caught at the security check-in. But criminal charges are left up to the agency that polices the airport.
Punishments also vary, from felony charges in Massachusetts — if the district attorney’s office decides to prosecute — to misdemeanors in some states, to no charges in others.
The TSA said it assessed $1.7 million in civil penalties for firearms in carry-on bags last year. The agency does not track prosecutions.
In the case of the woman stopped at Logan last month, she and her husband first blamed one another. He thought she removed it, and she thought he had.
They were traveling to Greece for a monthlong vacation with their four children.
She will receive a court summons after she gets back from her trip, according to State Police.
David Rosenbloom, a professor of health policy and management at Boston University, said the memory-lapse excuse makes sense in states with relaxed gun laws, as unlikely as it may seem.
“People who have guns in states with expansive open-carry laws are carrying their guns,” Rosenbloom said. “They get ready to go to the airport and don’t think about it. They always have their guns on them.”
TSA agents at Hartsfield-Jackson Atlanta International caught 111 travelers carrying guns through the security check-in last year, the highest number of any airport in the nation.
A measure took effect in Georgia last month that loosens restrictions and allows owners to carry guns in unrestricted areas of airports, bars, churches, schools, and some government buildings, unless otherwise noted. Now, licensed gun owners won’t be arrested if they are caught with a gun at the airport’s security checkpoint.
Glenn Yorek, captain of the Houston Police Department’s airport division, said travelers rarely attempt to conceal guns in their bags, and he believes they simply forget about the weapons.
In these instances, people with concealed weapons permits, no outstanding warrants, and a clear criminal history are allowed to take the gun back to their car or pass it to a relative who can take it off airport grounds. The district attorney does not typically press charges, Yorek said.
About 19 million passengers depart from the Houston airport each year. Gun confiscations aren’t a big issue for the agency because it happens so rarely, Yorek said.
“It’s not a high percentage, and this is Texas, by the way,” he said. “Everyone has a horse and a gun. These are not hardened criminals or terrorists and the DA has enough trouble.”
It would become a more serious issue if TSA agents began missing guns, but Yorek is confident that isn’t happening in Houston. Although it may be in Phoenix.
Earlier this summer, officials at London’s Heathrow Airport discovered a loaded Glock in the carry-on of a traveler who had flown in from Phoenix. The gun was found as he went through security to catch a connecting fight to Paris, according to news media reports. There were no incidents with the gun.
“The reality is that guns have no place on the aircraft, and our officers are there to enforce that,” Borer said. “We expect back up from law enforcement, and we don’t always get it.”
contributed to this report. Taryn Luna can be reached at email@example.com. Follow her on Twitter @TarynLuna.