The 29-year-old heiress was on a Delta flight from Los Angeles to Maui when she was forced to get back off and return to LAX.
According to TMZ, Hilton told how a 4-inch serrated knife was found in the seat pocket by another passenger and pointed out to a flight attendant, who then notified security.
All the passengers were told to get off the plane while security checked the aircraft to see if there were any more weapons.
Hilton and boyfriend Cy Waits were in the first class cabin and after getting off the plane, they were later let back on and allowed to continue their journey.