His real name is unknown, his age is unknown.
http://www.crimelibrary.com/criminal_mind/scams/DB_Cooper/index.html
"In either case, D.B. Cooper's nom de crime—no one knows his real name—may be the most recognized alias among western felons since Jack the Ripper."
http://www.crimelibrary.com/criminal_mind/scams/DB_Cooper/7.html
"The Air Force scrambled up two F-106 fighter jets from McChord. Those pilots were instructed to follow at a safe distance and watch for a jumper. But the fighters are built to fly at speeds of up to 1,500 mph. They were useless in slow-motion, low altitude surveillance. The authorities tried to recover by sending up a slower-flying Air National Guard Lockheed T-33, but Cooper probably had already jumped by the time it arrived."
http://www.crimelibrary.com/criminal_mind/scams/DB_Cooper/8.html
"The discovery of the cash gave impetus to new searches in that area until nature intervened. On May 18, 14 weeks after the bundles were found, the volcanic eruption of Mount St. Helens carpeted the region with a thick coating of ash and touched off vast fires. Many fear the eruption may have permanently obscured additional Cooper clues that may have been waiting in the Woodland vicinity."
http://www.crimelibrary.com/criminal_mind/scams/DB_Cooper/10.html
"In 1995, for example, Duane Weber, a Florida antiques dealer who was dying of kidney disease, told his wife, 'I'm Dan Cooper.' After Weber died, his widow found a hidden wallet that indicated the man had had a previous life as one John C. Collins. His resume of wrongdoing included a bad conduct discharge from the Navy and six prison sentences, one of them served 20 miles from Sea-Tac Airport. The widow claimed Weber took her on an unexplained 'sentimental journey' in 1979 to a remote place in the woods of Clark County, Washington. She said the husband looked like the Cooper sketch, knew Seattle well, smoked cigarettes, drank bourbon, and sometimes talked in his sleep about aft stairs and fingerprints."