The 81-year-old star of TV's "Golden Girls" was about to board a Cape Air flight when a security agent found the article in her belongings, World Entertainment News Network reported.
A fellow passenger said: "She started yelling that it wasn't hers and said 'The terrorists put it there.' She kept yelling about the 'terrorists, the terrorists, the terrorists.'"
After the knife was confiscated, Arthur pulled a key ring from her bag and told the agent it belonged to the "terrorists," before throwing it at them.
"Miss Arthur was cracking jokes and was a real character," a Cape Air spokeswoman told WENN.