"Air Canada flight AC837 flying from Madrid to Toronto had an engine problem shortly after taking off. A tyre also blew out on takeoff, one of 10 on this model of plane," the airline said in a statement to AFP.

"The plane chose to turn around and go back to Madrid. It is currently circling the skies to burn off fuel to reduce weight before landing."

It said the plane, which had 128 passengers on board, was a Boeing 767-300 that was designed to be able to function on one engine, but that an emergency had been declared "to ensure priority landing".

ENAIRE, the public body that manages air navigation in Spain, said on Twitter that the pilot had informed them he was "expecting to land at around 7:30 pm" (1830 GMT).

Spain's defence ministry confirmed to AFP that an F-18 had been scrambled to check on the landing gear.

"It's a support mission to see if the plane's landing gear is in good condition," a spokeswoman said, without giving further details.

Spanish airport authority AENA said Barajas airport had been informed about the plane's imminent return and was prepared to handle the situation.

Spain's emergency services also confirmed they had deployed rescuers and medics to the airport as a "preventative measure" and were closely coordinating with the airport authorities and other regional services.

According to the airport's website, Air Canada flight AC837 took off at 2:33 pm (1333 GMT), destined for Toronto.

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