The FBI says it has released new information it hopes will jog someone's memory and help them determine who the legendary skyjacker Dan Cooper, who bailed out of a commercial jet over southwest Washington in 1971, really was.

The man calling himself Dan Cooper, also known as D.B. Cooper, boarded a jet in Portland for Seattle the night of Nov, 24, 1971 and commandeered it, claiming he had dynamite.

In Seattle he demanded and got $200,000 and four parachutes and demanded to be flown to Mexico. Shortly before reaching the Oregon border, it is believed, he jumped with two of the chutes, one of which was a trainer and sewn shut.

Agents say they are almost certain he didn't survive.

"Diving into the wilderness without a plan, without the right equipment, in such terrible conditions, he probably never even got his chute open," Seattle-based agent Larry Carr said.

Carr is taking a new look at the decades-old mystery.

On Monday the FBI posted pictures they say are probably closer to what Cooper looked like.

"Who was Cooper? Did he survive the jump? We're providing new information and pictures and asking for your help in solving the case," the FBI said in a statement on Monday.

Several people have claimed to be Cooper over the years but were dismissed based on physical descriptions and, later, by DNA evidence recovered in 2001 from a cheap tie the skyjacker left on the plane. Within the first five years, agents considered about 800 people as possible suspects.

In 1980 $5,800 of the stolen money, in $20 bills, was found by a boy near the Columbia River. Abundant theories and leads have led nowhere.

Agents concluded long ago that he was not an experienced skydiver and almost certainly had no help on the ground, since he could not have known where he was jumping because of cloud cover.

"Maybe a hydrologist can use the latest technology to trace the $5,800 in ransom money found in 1980 to where Cooper landed upstream," Carr said. "Or maybe someone just remembers that odd uncle."

FBI release and pictures: http://www.fbi.gov/page2/dec07/dbcooper123107.html