An Air Canada plane was forced to make an unexpected landing in Ireland on Monday after the co-pilot became ill in the cockpit, the airline said Tuesday.

But Air Canada would not confirm media and passenger reports that the co-pilot had needed psychiatric care, forcing the plane to land at the Shannon airport, west of Limerick. The plane had taken off from Toronto and was scheduled to land in England.

Canadian passenger Seàn Finucane told CBC News that the co-pilot started to act distraught about an hour before the flight carrying 146 passengers was scheduled to land at London's Heathrow Airport.

"He was yelling loudly at times," Finucane said, explaining that the co-pilot's voice was clear and he didn't sound drunk.

"When they tried to put his shoes on later, for example, he swore and threatened people … He was swearing and asking for God, and was very, very distressed."

Airline spokesman Peter Fitzpatrick said Air Canada can't provide details about personnel issues. He would only confirm that the captain made the decision to divert to Shannon shortly before 8 a.m. local time.

"The aircraft landed without incident," Fitzpatrick said. "At no time were the safety of the passengers or crew in question."

The Irish Independent reported that the co-pilot of Flight 848 was forcibly taken off the Boeing 767 airplane by fellow crew members and a passenger who is a member of the Canadian Forces.

The newspaper, quoting officials at Shannon International Airport, said the co-pilot was admitted to the psychiatric unit of the Ennis General Hospital in nearby County Clare.

Air Canada confirmed the co-pilot is in hospital, but would not comment on what type of treatment he is receiving or when he might be released.

Passengers taken to hotels

Air Canada said the 146 passengers on board were allowed to disembark shortly after the incident.

Patrick Flynn, a freelance journalist in Shannon, said passengers were taken to local hotels after the plane landed. A second Air Canada plane arrived at Shannon airport from London's Heathrow Airport less than five hours later with a replacement crew, said Flynn.

Shannon Airport Authority spokesperson Eugene Pratt said the flight arrived in London about eight hours later than scheduled.

"An Air Canada crew flew in here yesterday and took the aircraft on to London to complete the trip," he said.

Transport Canada will conduct interviews

Pratt, who called the incident "irregular," said about a dozen flights end up diverted to Shannon each year because of technical, mechanical or health problems.

He said it wasn't an emergency landing, but paramedics and a doctor were called to the airport to meet the plane when it landed and assess the co-pilot.

Transport Canada will be interviewing the flight crew and the airline, spokeswoman Lucie Vignola said Tuesday, noting that it appears proper procedures were followed.

She said commercial pilots must undergo medical checkups every six months under the requirements of their licence.

With files from the Canadian Press