An Air Canada flight from Toronto to Turkey made an unscheduled landing at Heathrow Airport in London, England, early Saturday morning.

Flight AC 810 was enroute to Istanbul's Ataturk International Airport when the flight crew became aware of a low oil quantity indication, Air Canada spokesperson Isabelle Arthur told CTV News.

Crew members decided to divert to Heathrow Airport as a precaution. Emergency services were advised, following standard operating procedure.

The flight, which took off from Toronto at 4:50 p.m. on Friday, landed in London at 5:38 a.m. local time (12:38 a.m. ET). The remainder of the flight was cancelled so the plane could be inspected, and passengers were booked on other flights.

Saturday's return flight, AC 811, was also cancelled.

Passengers took to Twitter to express their frustration: