Simran Johal distinctly remembers hearing "a clunky noise" while aboard Air Canada Flight 864, as she headed back to London via Montreal on Sunday night after a holiday with her sister in Cancun, Mexico.

The Airbus A330, carrying 294 passengers, lost a wheel as it was taking off from Montreal's Trudeau International Airport, Air Canada confirmed to CBC.

The wheel was one of the eight main-gear wheels located under the plane's wings.

Johal said the flight was plagued by turbulence when she and her sister heard the noise. "Why is it shaking so much?" she said her sister kept asking. "I kept reassuring her."

The airline didn't alert passengers to anything being wrong, Johal said, adding that she only found out about the missing wheel when she saw her flight mentioned on the local news during her taxi ride home.

​"Thank God it wasn't a worse situation," said Johal. "At the same time, it's a poor effort for Air Canada that this wasn't checked properly."

2nd time this year

In an emailed statement, Air Canada spokesperson Isabelle Arthur told CBC that preliminary information shows the wheel separated from the plane while it was taxiing down the runway, preparing to take off.

It was unclear whether the pilot knew about the missing wheel prior to takeoff.

In February, an Air Canada Airbus A330 sustained wheel damage prior to takeoff and was grounded in Brussels. (Submitted)

Because the landing gear has ten wheels — four under each wing and two nose-gear wheels — Arthur said a missing one didn't cause any issues.

The plane is being repaired, she said.

In February, another Air Canada Airbus A330 was grounded while preparing to depart from the airport in Brussels due to damage to its wheels.

"We maintain our fleet to the highest standards, and these two events are isolated," Arthur said in the email.