Cooper exited the aircraft via the center rear door, hit 300+ knots of windstream and went ass over teakettle wrapped in his chute like a tamale, then died on impact like a badly delivered order from the butcher shop. SPLAT!
Unlikely. Immediately, and for many years after the hijacking, literally hundreds of treasure seekers scoured every known forest, hillside and riverbank throughout the flight path.
If he was laying dead somewhere, he would of been found.
I'm not drawing any conclusions other than I believe he landed alive.