An Easyjet flight was forced to turn back just minutes before takeoff after a passenger spotted a spanner wedged in the wing.
The plane had already taxied and was preparing to takeoff for the flight from Geneva to Copenhagen when a Swiss man noticed the tool.
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Christophe, 25, told cabin crew immediately and the pilot turned back towards the terminal.
According to the Metro, Christophe said: "I realised straight away that what I was seeing was not normal. There was a spanner attached to the wing."
The Sun reports that an Easyjet spokesman said: "The captain returned to the plane's departure point and a spanner was discovered.
"We have opened an inquiry and the authorities have been informed."
Following checks, the flight took off for Copenhagen an hour later.
According to the Daily Mail, an aviation expert told the 20 minutes online website in Switzerland: "With the vibrations from the acceleration, the tool could have fallen onto the runway, and then been hit by the next aircraft.
"It could have caused serious structural damage, just like with the Concorde crash in Paris.
"If it had stayed attached to the plane, the pilot would have realised when he retracted the flaps about 400 metres from the ground, and been forced to make an emergency landing."
The expert was referring to the crash of An Air France Concorde in July 2000, which killed 113 people. It was believed to have been caused by a strip of metal from a Continental Airlines DC10 which fell onto the Charles de Gaulle airport runway and punctured the jet's tyres.
Rubber fragments were sent flying into a fuel tank, setting it on fire and sending the Concorde hurtling into a hotel several miles away.