A Delta Air Lines passenger managed to slip a gun through airport security and onto a flight from Atlanta to Japan before alerting the airline crew at his destination, officials said.

The passenger carried the firearm through Hartsfield-Jackson Atlanta International Airport to Narita, Japan, on Jan. 2, the Transportation Security Administration said in a statement that acknowledged security procedures weren’t followed.

“Upon the customer’s disclosure, the airline reported the incident to TSA,” a spokesperson for Delta told HuffPost in an email.

The TSA said its security checkpoint was fully staffed and unaffected by the partial government shutdown that has prompted some security staff to call in sick to protest working without pay. Standard procedures weren’t followed, the agency said.

“TSA will hold those responsible appropriately accountable,” the agency said of the screening that failed to discover the weapon.

A representative for the Atlanta airport did not immediately respond to a request for comment on Monday.

TSA employees have worked without pay since Dec. 22 amid what has become the longest federal shutdown in the nation’s history.

The shutdown prompted the Houston Bush Airport to close one of its TSA checkpoints on Sunday because of a lack of staff. Miami International Airport also closed one of its concourses for half of the day on Saturday and Sunday for similar reasons.

Firearms are discovered in carry-on luggage with alarming frequency.

ASSOCIATED PRESS One of 30 guns confiscated at Hartsfield Jackson Atlanta International Airport security checkpoints in May is pictured. The collection set a new record for most guns discovered at a single airport nationwide in a single month.

A record of 30 firearms were confiscated in May from passengers at Atlanta’s airport. During one week last month, the TSA reported finding 78 firearms ― 63 of them loaded ― at airports nationwide.

Authorities say it’s extremely rare for a gun to get past security. Still, the TSA in 2015 investigated a report of a Georgia man carrying a loaded gun through the Atlanta airport security and onto a plane headed to Chicago. The man said he mailed his gun home once he reached his destination and realized what he had done, WGCL reported.

Atlanta’s airport is the busiest in the country, seeing 103.9 million people each year, according to website World Atlas.