* this was the only unsolved aviation hijacking in U.S. history.

* Cooper claimed he had a bomb and threatened to blow up the plane if his demands were not met. His ransom note read: "I have a bomb in my briefcase. I will use it if necessary. I want you to sit next to me. You are being hijacked." To prove his point, he later opened the briefcase for a short moment for the flight attendant to notice red cylinders, a large battery, and wires, convincing her the bomb was real.