Three times in recent years, intruders got past the security fencing that surrounds Honolulu Airport, according to an Associated Press investigation.

In 2012 airport employees found an injured 27-year-old woman lying in a culvert inside the security fence line.

In 2013 a woman entered airport property through an exit gate, and a 40-year-old man said he had climbed a fence to reach the airport operations area. Authorities issued an unauthorized-entry citation and took him for medical observation.

Airports say breaches are relatively rare. Security measures typically include fences, cameras and patrols, but there are gaps. Not all of the miles of fences are routinely patrolled or covered by video surveillance.

But they do happen, and not just in Honolulu.

Between January 2004 and January 2015, there were at least 268 perimeter security breaches at 31 major U.S. airports, the AP 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.

Due to Hawaii’s rules for how long official documents must be kept, officials at the state Department of Transportation said they would not have records prior to 2012 if a breach did not result in a police investigation.

In a search of media reports, AP identified a fourth breach: In 2004 the Honolulu Star-Bulletin reported that a 17-year-old Hawaii Kai boy rammed his sports car through a locked airport security gate as he fled a traffic stop.