A passenger made it through a Transportation Security Administration checkpoint with a gun on Jan. 2, boarding a Delta Air Lines flight at Atlanta Hartsfield-Jackson International Airport and flying to Tokyo, authorities said Sunday.

TSA confirmed the incident in a statement Sunday night but denied it was related to callouts stemming from the government shutdown, as hundreds of airport screeners are working without regular pay.

“TSA has determined standard procedures were not followed and a passenger did in fact pass through a standard screening TSA checkpoint with a firearm,” the agency said of the incident. “TSA has held those responsible appropriately accountable.”

Delta said the incident occurred aboard flight DL 295 from Atlanta to the Tokyo region’s Narita International Airport on Jan. 2, and as soon as the passenger reported carrying the firearm, the airline disclosed the offense to TSA.

The agency said the passenger was cooperative and “was met by Japanese authorities upon landing. "

The incident came days after a reported uptick in callouts from TSA staffers, leading some to speculate that the screening mistake was related to the government shutdown. But TSA strongly denied any connection, saying the percentage of callouts on Wednesday, Jan. 2 was 5 percent, the same percentage who called out a year prior on Wednesday, Jan. 3, 2018.

TSA Administrator David P. Pekoske announced Friday that agency employees will receive a day’s pay if they worked on Dec. 22, and uniformed officers will also net a $500 bonus for their efforts during the holidays — paychecks to be received by Tuesday, the agency said.

TSA screeners stop passengers — many of them forgetful or unwittingly — carrying loaded guns onto planes in their carry-on luggage fairly regularly throughout the year; a reported 4,000 firearms were seized at checkpoints in 2017. Instances in which armed passengers make it through security, however, are rare.

Staffing issues prompted Houston’s George Bush Intercontinental Airport to close one of its TSA screening lines on Sunday, according to media reports. Miami International Airport closed one of its concourses for half the day on Saturday and Sunday, and airport officials said they plan to do the same Monday out of concerns they wouldn’t have enough employees to operate all the security checkpoints.