"The guy didn't want to stay in his seat," said Henna Solamaa, a traveler from Finland who was aboard the Airbus 330 on Sunday.
Passengers apparently saw no cause for concern until the man got up to go to the bathroom after crew members told passengers to stay in their seats for the last hour of the flight. Witnesses said people seemed more concerned that somebody was defying crew orders, not that the man seemed suspicious.
Tim Jeronimus said crew members banged on the bathroom door several times, and the passenger refused to get out.
The Jeronimus family was sitting near the passenger. They were returning home to Ann Arbor, Mich., from a visit with relatives in the Netherlands.
Just two days earlier, Umar Farouk Abdulmutallab, 23, attempted to destroy a plane by igniting an explosive on his body shortly before arrival in Detroit, the FBI says. Passengers pounced on him to extinguish the flames.
That scare has led to new security rules that were a factor in Sunday's incident. Passengers were told to stay in their seats and keep their laps clear for the final hour.
"Even if you're sick, you have to pay respect to what the flight crew is saying," said Robert Ficano, Wayne County chief executive.
Gregory Tucker, 42, of The Hague, Netherlands, said he didn't see or hear any disruption.
"It didn't seem particularly effective," Tucker said of the new security rules.
Hitesh Desai said he was anxious throughout the incident.
"It does feel surreal that this is happening," Desai, 45, of Rochester Hills, Mich., said later.
Ed White reported from Detroit. Associated Press videographer Bill Gorman in Detroit and writer Devlin Barrett in Washington contributed to this report.