An Air Canada flight was due to make an emergency landing in Madrid on Monday following a technical problem just hours after taking off from the city's Barajas airport, aviation officials said.
"Plane with a technical problem is overflying Madrid before returning to Barajas airport," tweeted ENAIRE, the public body that manages air navigation in Spain, saying it was a flight which had taken off for Toronto.
An ENAIRE spokesperson said the plane was dumping excess fuel before landing.
"It is an Air Canada plane that took off from Barajas where it had just fuelled up and protocol demands it dump fuel before landing, which is what it's doing now," she told AFP.
She said the plane turned back after "technical problems", saying it had a "blown-out tyre" and possibly engine failure.
It was not immediately clear how many passengers were on board.
According to the airport's website, Air Canada flight AC 837 took off at 1433, destined for Toronto.
Spanish airport authority AENA said Barajas airport had been informed about the plane's imminent return and was prepared to handle the situation.
Earlier in the day a drone sighting had caused disruption at the airport, with 26 flights being diverted from the airport.