Armed officers rushed aboard the same Detroit-bound Northwest Airlines flight that was attacked on Christmas Day, after an emergency call from the crew about another Nigerian on board.
But the perceived threat turned out to be an ill traveller who spent too much time in the bathroom.
Coming so soon after Nigerian Umar Farouk Abdulmutallab was accused of trying to blow up a plane, authorities quickly responded to an emergency call from the crew on Flight 253 from Amsterdam.
Some of the 256 passengers were alarmed, while others apparently were not aware of the incident.
Tim Jeronimus, 13, said he was “a bit nervous” when officers entered, and his 11-year-old sister, Emma, said she was scared.
Their mother Jane said the captain told passengers that no arrival gates were available.
“I said to my husband, ’That’s not true’,” she said later inside the terminal at Detroit Metropolitan Airport. Airport police and border officers then entered the cabin to remove the man from the plane.
Passengers were safely evacuated and luggage was lined up on the ground for inspection by bomb-sniffing dogs.
The passenger, also a Nigerian, was a businessman who was sick and posed no security threat, said two law enforcement officials.
The man had “spent a lengthy time in the restroom”, FBI spokeswoman Sandra Berchtold said.
“This raised concerns so an alert was raised. ... The investigation shows that this was a non-serious incident and all is clear at this point.”
The passenger was released after questioning, she said.
The man used the bathroom several times during the trip and refused to come out as the plane was preparing to land, said Lester Robinson, head of the Wayne County Airport Authority.
“The guy didn’t want to stay in his seat,” said Henna Solamaa, a traveller from Finland who was aboard the Airbus 330 yesterday.
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.