The FBI's file on D.B. Cooper has remained open since the skyjacking. Over the years, several agents have taken charge of the case, followed leads, retired and passed it along. More than 800 suspects have been evaluated [source: NPR]. About 20,000 documents and pieces of evidence were accepted, catalogued and stored [source: Seattle Post-Intelligencer]. None have led to a solution to the case.
FBI profilers created two sketches of Cooper early on in the investigation. One was a drawing of the man, generated from descriptions given by two stewardesses aboard the flight. Over the years, agents have stood by this depiction of the hijacker. Both women gave almost identical descriptions of the man who called himself Dan Cooper, and each woman was interviewed separately in two different cities [source: FBI].
The other sketch was a profile of Cooper's character. To undertake such a daring plot, he would have to be a trained parachutist, perhaps a paratrooper. He drank bourbon and chain-smoked cigarettes on the flight. He was polite and mild-mannered. His only threat came when he demanded the money and four parachutes: "No funny stuff or I'll do the job," he allegedly told the crew [source: The Independent]. No one was harmed in any way on the flight. He released the passengers even before receiving the ransom.
As new technology has emerged, it's been used in the Cooper case. The skinny, black clip-on necktie Cooper wore during the hijacking was left behind when he jumped. The FBI was able to cull a DNA sample from it, which ruled out at least one of the suspects who've emerged over the years -- a man named Duane Weber.
In 1996, Weber's widow told the FBI that her husband confessed to being Dan Cooper on his deathbed. She was unaware that Dan and D.B. Cooper were one in the same, and shrugged the confession off [source: U.S. News and World Report]. She was convinced that her husband had been the famed skyjacker until he was ruled out by DNA evidence in 2001.
Many FBI detectives (including one of the case's former lead agents) have fingered a man named Richard McCoy as Cooper. Five months after Cooper hijacked the Northwest Orient flight, McCoy -- a Vietnam veteran and former Sunday school teacher -- pulled a similar heist, jumping out of a plane over Utah with $500,000 in cash. He was soon caught, however, and sentenced to 45 years in prison [source: FBI]. McCoy escaped in 1974 on the back of a garbage truck and died after being shot by police [source: New York Magazine]. The hitch? McCoy didn't fit the stewardesses' description.
In 2007, Kenneth Christiansen emerged as a suspect. Christiansen's brother, Lyle, was convinced that Kenneth was D.B. Cooper. Lyle began a letter-writing campaign to Nora Ephron, a movie director, to share his story. New York Magazine published the story of Lyle's campaign in October of the same year. Kenneth Christiansen fit Cooper's profile in many ways -- he also looked a good bit like Cooper and was an employee of Northwest [source: New York Magazine]. The FBI has rejected him as a suspect, however.
One unlikely suspect is Bobby "Barbara" Drayton, who's thought to be the first gender-reassignment recipient in Washington state. Drayton confessed to the Cooper heist, but recanted later. Her friends still consider her a suspect, believing that she disguised herself as a man during the hijacking [source: Seattle Post-Intelligencer].
The FBI has discounted many suspects. Mysteriously, the real identity of D.B. Cooper remains unknown. Could he still be alive? Find out on the next page.