An airplane travelling from Toronto to Sao Paulo, Brazil was forced to turn around about halfway through its flight after it was discovered that a passenger on board slipped through without proper security clearance.

Authorities first noticed something was amiss back at Pearson International Airport when they were alerted to a man breaching security. Flights out of Terminal 1 were grounded while they searched for the man but authorities, who had pictures of the suspect from surveillance cameras, soon realized he made it onto a flight.

Air Canada flight AC 090 was in the air for four hours when the pilots were asked to turn around and return to Pearson. The flight had taken off at 11:30 p.m. from Toronto and was supposed to last about 10 hours and 38 minutes.

According to a passenger who was on the plane, a "young man" was escorted out by police as soon as the flight landed at Pearson.

"He seemed really calm. He looked just fine," said Chantal Vallee, a coach with the University of Windsor, in an interview with CP24. "He quietly walked back with police officers out of the plane."

Vallee said the flight crew was careful in the way they alerted passengers.

"I was alseep like most passengers (when the announcement was made)," she said. "Shortly before 5 a.m. the pilot says we are an hour away from landing back in Toronto. We were told there was a concern from the Brazilian governmnt that we weren't legally allowed to land."

Vallee said immediately passengers began to dream up scenarios about what would prompt the concern.

"I thought something must have happened with the World Cup or something with the manifestations that are going on in Brazil," she said. "We had no idea."

Meanwhile back at Pearson, a regular schedule has resumed for all grounded flights and the 189 passengers on board the Sao Paulo flight are preparing for another long journey.

Peel police said Thursday afternoon that the passenger in question has been identified and interviewed and that investigators have concluded that there was no criminal element in his actions.

Earlier reports suggested the man slipped past security in the pre-boarding area of the airport for a quick cigarette but officials have yet to confirm the details of the breach.

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