The Transportation Security Administration caught more firearms at airport checkpoints in 2019 than in any other year since it was created in 2001, the agency said Wednesday, as part of a steady uptick that its leader called “deeply troubling.”

The agency said that it found 4,432 firearms last year in carry-on bags or carried by passengers, neither of which is allowed. That number was 5 percent higher than the 4,239 firearms discovered in 2018, and nearly five times the 926 found in 2008, the T.S.A. said.

A vast majority of the guns found in 2019 — almost 90 percent — were loaded, the T.S.A. said. About one-third of the guns caught had a round in the chamber.

“The continued increase in the number of firearms that travelers bring to airport checkpoints is deeply troubling,” David P. Pekoske, the administrator of the T.S.A., said in a statement on Wednesday. He advised fliers to follow the rules of the “proper way to travel safely with a firearm.”