The statute of limitations on D.B. Cooper’s crime expired a few years ago. The FBI made an announcement that they considered the case closed and would do no more investigation.
No one ever proposed a possible D. B. Cooper who disappeared for the right amount of time as an actual suspect. I think the reason no one ever found D.B. Cooper is that we were all looking in the wrong place. The real D. B. Cooper was Canadian. The name D. B. Cooper comes from an error in the early press reports. The actual hijacker used the name Dan Cooper. Dan Cooper is the name of a Canadian comic strip that was mostly unknown in the US at the time. That Dan Cooper was a flying ace and Soldier of Fortune.
https://en.m.wikipedia.org/wiki/Dan_Cooper_(comics)
I think D. B. Cooper was an unknown Canadian adventurer who read too man SOF articles and died in his descent and who was never found and not missed because no one was looking for a Canadian D. B. Cooper.
But this is one of the mysteries that is best left unsolved. For all we know D. B. Made it safely to the ground and hiked to Los Vegas where he spent the rest of his life wasting his fortune at the blackjack tables, gorging himself at the buffets and . . . Raging about MOTHER?
TABS, where were you in November of 71? We know that in 1969 you were at Altamont. All on the west coast . . . men of wealth and taste . . . a coincidence? I think perhaps not!