Air Canada flight to Montreal turns back to Heathrow shortly after departure

An Air Canada flight bound for Montreal turned back over the Atlantic on Monday afternoon and landed at London Heathrow about two and a half hours after it left, according to the airline and flight tracking data.

Flight AC865, an Airbus A330-300 registered C-GKUG, departed Heathrow at 2:00 PM BST on a scheduled seven-hour service to Montreal-Trudeau International Airport. It climbed to 34,000 feet, crossed Ireland and began its oceanic transit before the crew decided to abandon the crossing.

Tracking data showed the wide-body jet making a 180-degree turn over the water and retracing its route across the British Isles. It touched down on Runway 27R at Heathrow about two hours and 30 minutes after departure.

Air Canada gave a reason other than the mechanical trouble or medical emergency that commonly prompts such turnbacks. The carrier rescheduled the flight for a 6:00 PM BST departure and told passengers the delay stemmed from "immigration, customs, or health measures."

No emergency was declared and the aircraft landed without further incident. Passengers stayed at Heathrow while staff worked through the regulatory requirements and readied the aircraft for a second departure attempt.