**Kenneth Christiansen** was a Northwest Orient flight purser and paratrooper who attracted attention after his death in 1994. His brother Lyle eventually came forward with information suggesting Kenneth had made a deathbed remark implying awareness of a secret—though the exact words and their meaning are disputed. Kenneth had also, in the years after 1971, purchased a house with cash, which some researchers found suggestive. The FBI examined the Christiansen theory and has not publicly confirmed or excluded it with finality, but has noted that Christiansen’s physical description does not closely match the witnesses’ composite.
**Robert Rackstraw** was a pilot, paratrooper, and convicted felon who was investigated as a Cooper suspect and publicly named in a 2016 book. His attorney denied the claim. Rackstraw died in 2019 without being charged.
**Sheridan Peterson**, a former Boeing engineer and skydiver, was not interviewed by the FBI until decades after the hijacking despite being raised as a possible suspect early on. He told investigators he had been in Nepal at the time of the hijacking. He has blue eyes, which does not align with some witness descriptions. Peterson has denied any involvement.
The common thread in all of these suspect discussions is the same: physical description that doesn’t quite match, alibis that can’t be fully verified or challenged, and an absence of any direct physical evidence connecting any specific individual to the flight, the ransom, or the jump.
No one has been arrested. No one has been charged. No one has been convicted.