CHICAGO (AP) — Chicago’s airports have experienced five breaches of perimeter security over the past 11 years, including one this January when a man armed with a pistol drove past a checkpoint.

Nationwide, there have been at least 268 perimeter security breaches at 31 major U.S. airports from January 2004 through January 2015, an Associated Press investigation found. Incidents ranged from fence jumpers taking shortcuts and intoxicated drivers crashing through barriers to mentally ill intruders looking to hop flights. None was terrorism-related.

Airports say breaches are relatively rare. Security measures typically include fences, cameras and patrols, but there are gaps.

Chicago’s Department of Aviation identified three breaches; AP found two others through news searches. Among the incidents was:

— O’Hare International, Jan. 14, 2015: A man who drove through a security checkpoint as the gate arm was raised told authorities he was trying to bypass train tracks. He said he had a concealed weapon permit and officers found a loaded pistol.

— O’Hare International, March 5, 2012: An escaped prisoner jumped a fence and ran around the airfield for 12 minutes as authorities chased him.

— O’Hare International, Oct. 7, 2010: A man pushed down razor wire atop a perimeter fence and went over with his bicycle. Airline employees saw him and offered him a ride in their van. He declined and eventually made it to a terminal door. A gate agent let him in, and police arrested him.

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