The passenger was restrained after he became disruptive, saying all fellow travelers had been poisoned by the food served on the aircraft, a Boeing 777, CBS News reported.
After landing the plane taxied to a remote area of the airport, where police and FBI boarded, before it was towed to a terminal to allow passengers to disembark, The (Newark) Star-Ledger reported.
The incident occurred several hours before the flight was due in Newark. The unidentified passenger, a man, stood up and screamed, "We're all being poisoned. You've all been poisoned," the FBI said.
Passenger Jacques Roizen of New York said he was in his seat when the man began screaming. Roizen said the man sounded paranoid and railed about national defense and poisoning.
"He was afraid of the FBI and afraid of being killed, and wanted the plane diverted to Canada," Roizen said.
A statement from United Airlines said the aircraft's crew followed procedures and got the situation under control.