NEW YORK -- A Southwest Airlines co-pilot was arrested Monday at an airport in New York state after authorities discovered a gun loaded with six bullets in his carry-on, the Transportation Security Administration said.

The agency’s officers found the .380 caliber handgun, which was among the co-pilot’s carry-on items, as he entered the Albany International Airport checkpoint, the TSA said in a news release. It was detected by an X-ray machine.

The Albany County Sheriff’s Deputy assigned to the checkpoint was contacted, and the co-pilot was arrested on a weapons charge. The flight — headed for Chicago — was delayed for about four hours.

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The TSA said the incident marked the second time in less than a month that TSA officers detected a firearm at the Albany airport. In late March, the agency found a loaded .45 caliber handgun in a passenger’s carry-on bag.

TSA officers at the same airport found two guns in 2016.

Last year, a record number of firearms — 3,391 — were discovered in carry-on bags in the U.S., the TSA has said. Eight-three percent of firearms found at TSA checkpoints last year were loaded.

“As a reminder, firearms, firearm parts and ammunition are not permitted in carry-on bags, but can be transported in checked bags if they are unloaded, properly packed and declared to the airline,” the TSA said Monday in its news release. “Individuals who bring firearms to the checkpoint are subject to possible criminal charges from law enforcement and civil penalties from TSA of up to $12,000.”