Saw an interesting article about D B Cooper in Air and Space mag.
Added my 10c:
While everybody wants to believe that D.B. Cooper got away I think he died on the night. I'm a former skydiver with over 450 jumps, including one from a a Boeing 727 at the World Freefall Convention.
The first odd thing is that D.B.Cooper was apparently wearing slip on shoes. No skydiver in 1971 would have jumped wearing such shoes - landings were fast at the best of times and you needed ankle protection. Any experienced jumper who was planning this would have had footwear with proper ankle protection.
But the part which makes it obvious to my mind that Cooper wasn't an experienced jumper was that he didn't bring a parachute with him. Skydivers are understandably picky about equipment and any jumper planning a hijacking would prefer to bring his own equipment rather than rely on the government to provide it to him. Not only did he create a dependency his plan didn't need, he also telegraphed his intentions. If, instead, he had disguised the parachute as a bomb and then left a suitably fractured and psychotic suicide note before jumping out the back with the money it would have taken people days - if ever - to figure out what he'd done.
The third thing I'm not so sure about - apparently he was seen using paracord to tie the money bag to himself. You need to be extremely careful about attaching anything to yourself and especially an object that is loose or can move. Simply failing to secure the chin strap on your helmet results in agony as it beats against your skin in the 120kt airflow. Attaching a large object and then being able to fall cleanly and not tumble - which is essential for a safe opening - would require practice. Instead he was almost certainly an amateur who left the plane, lost his shoes, tumbled wildly while trying to open his borrowed parachute and then spent the rest of his life regretting it...