In a statement Air Canada Boeing Co said, a Boeing 737-8 Max suffered an engine issue en route between Arizona and Montreal, forcing the crew to divert the aircraft to Tucson, Arizona.

Shortly after the take-off, the plane’s pilots received an “engine indication” and “decided to shut down one engine,” said a spokesman for Air Canada. “The aircraft then diverted to Tucson, where it landed normally and remains.”

The incident took place on December 22, 2020.

In a report, Belgian aviation news website Aviation24.be said, the crew received a left engine hydraulic low pressure indication following which they declared a PAN emergency before diverting the flight.

“Modern aircraft are designed to operate with one engine and our crews train for such operations”, said Air Canada in a statement.

Following the MAX’s return after a 20 month safety grounding, Boeing and operators are bracing for heightened scrutiny; according to experts such glitches are common and typically go unnoticed.

The Boeing 737-8 MAX was grounded after two fatal air crashes linked in part to flawed cockpit software. The engines were not implicated.

Last month, the United States lifted a 20-month-old flight ban on the 737 MAX with the U.S. Federal Aviation Administration outlining details of the software, system and training upgrades Boeing and airlines must complete before carrying passengers.