The missing ingredient: gravity

Big deal. Forty years later, why are we still so fascinating in a guy we don't know, who ransomed a commercial plane for some money, jumped out over some woods, and was never seen again?

One answer: gravity.

"It is violent, inevitable, instantaneous and unmerciful," Dr. David Hubbard wrote in The Skyjacker, an influential psychological study published the same year of the Cooper hijacking. For his study, Hubbard interviewed countless hijackers, studied their motives and discovered that, more or less, the hijackers had issues with that force that binds us all since birth.

"It is indifferent and final," Hubbard wrote of gravity.

So what makes the skyjacker that parachutes out of jet different than a bank robber that speeds off in a car is not only the stylish and romantic getaway. It's the attempt to challenge, conquer and break free from a force that governs us all every moment we have and refuses to let go.

Whoever Cooper was, he had a desire to defy gravity, the ultimate expression of rebellion, according to Hubbard. It's a desire we share with Mr. Cooper, and another reason why we want to know more about him.