Victor Torres-Rivera went through security screening with a 5-inch ceramic knife. It was detected on his flight home from Newark.

Sources said Torres-Rivera told them that he carried the knife for protection and simply forgot that it was in a day planner.

The Pfizer employee was not believed to be a terror threat, but he was arrested on suspicion of misdemeanor weapon possession, sources said.

The TSA did not immediately comment.

“Mr. Torres-Rivera, who was released … is cooperating fully with law enforcement,” a Pfizer spokesman said.