An Air Canada Boeing 737-8 MAX flying from Arizona to Montreal with three crew members on board experienced an engine problem that forced it to land in Tucson, the airline said Friday.

Shortly after taking off on December 22 the pilots “received an engine notification and, according to the standard operating procedure for such a situation, they decided to shut down an engine,” Air Canada said in a statement written in French.

“The aircraft was rerouted to Tucson, where it landed normally and remains,” Air Canada said, without specifying the nature of the malfunction, which occurred during a non-commercial “positioning flight.”

According to the Belgian specialist site Aviation24.be, which first reported the emergency landing, the malfunction was due to a drop in hydraulic pressure in the left engine.

The Canadian government announced in mid-December that it had approved the design changes Boeing made to 737 MAX planes after two crashes that killed 346 people led to the aircraft being grounded.But the aircraft, purchased by the Canadian airlines Air Canada, Westjet and Sunwing, has not yet been authorized to make commercial flights in Canadian airspace.

The US in mid-November authorized the MAX to fly again, but several modifications will have to be made to the aircraft before it can be returned to service, according to the Federal Aviation Administration.

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Two weeks ago, the Brazilian airline Gol became the first in the world to put the 737 MAX back into service.