The FBI met United Airlines Flight 116 as it landed at Newark Liberty International Airport Monday around 1:30 p.m., passengers said, and escorted the man off the airliner.
The man's name has not been released but passengers described him as American. Passengers said he started screaming about 9 hours into the 15-hour flight about being afraid of the FBI and fearing he was going to be killed. He asked that the flight be diverted to Canada.
"He was clearly not stable," said passenger Jacques Roizen of New York, who helped wrestle the man to the cabin floor and sat in the same row as him after he was handcuffed.
Roizen said he and other passengers and a flight attendant jumped on the man and subdued him when he started reaching for his pockets hours. United said it followed its procedures for dealing with disruptive passengers and decided to continue the flight as scheduled.
Passenger Peter Jones of Washington said the passenger called out what he said was his name, his birthdate and his social security number several times, and claimed he worked for the U.S. Embassy in Abu Dhabi.
Jones said the man claimed to have information about Edward Snowden, a former government contractor who revealed a once-secret National Security Agency surveillance programs two weeks ago.
"He was just saying he had information relating to Ed Snowden and he was being taken back to some safe house somewhere, never to be seen again," Jones said.
A man who said he was on the same flight as the unruly passenger and recorded the incident with his phone played the audio for reporters. The passenger who recorded the clip did not wish to give his name. On the recording the man who caused the incident screamed and repeated "I'm dead" 23 times.
"Snowden? No, he's right! I know this now, I know this because of what just happened to me. He's totally right," the disruptive passenger said, then continued to rant about the NSA.
Jones said he never heard the man threaten passengers or the plane. While the plane was still in the air the FBI said the man had claimed everyone aboard the plane was being poisoned, but the agency later said it was working to clarify what the man said.
"He said something that people are going to poison him, that he was going to die," Jones said.
On the recording the man claimed to work for the government.
"You work for the CIA! If you work for the National Reconnaissance Office, you will not get a trial by jury. You will not get a trial by jury. They think I've done something wrong, put me in front of a judge," he said, "say I'm guilty."
In the audio the man claimed to be "dead already, they're gonna kill me."
Another passenger, Paula Shea of St. Petersburg, Fla., said the man claimed he was married to a Chinese spy.
While sitting in the same row as the subdued man, Roizen said he did his best to try to calm him.
"He was very paranoid," he said.
Associated Press writer David Porter contributed to this report.