A flight to London operated by China Eastern Airlines made an emergency landing when it suffered a mechanical failure mid-air and the pilots dumped fuel.

The MU533 flight departed from Shanghai Pudong International Airport, in China, bound for London Heathrow at around 9:39 am on Saturday, December 9.

But just an hour into the nine-hour-long journey, the pilot was forced to divert back to Shanghai due to a severe mechanical failure that prompted him to dump massive amounts of its fuel mid-air.

A video recorded by a passenger onboard the Airbus A330 with Rolls Royce engines shows the moment fumes burst out of the wing as the pilot released the fuel, as terrified travellers watched from the cabin.

Seconds later the pilot addressed them, saying: 'I am very sorry to inform you that due to mechanical failure, we are unable to fly to London as planned.

'We have now decided to return to Shanghai Pudong International Airport. Thank you for your understanding.'

An airline spokesman said that the plane landed safely at the airport at 11:43am and added that the nature of the aircraft's malfunction 'was not clear yet'.

The passengers were then transferred to a second, fully functional plane, that took off at 2:03 pm later that day.

The spokesman added: 'We have arranged for another aircraft to operate the flight, and it took off around 2 pm on the same day.

'The company quickly deployed resources and executed the aircraft replacement. We apologise deeply for any inconvenience caused to passengers.'

This is the airline's second flight malfunction last week, after a Hong Kong-bound plane made an emergency landing in the city of Xiamen, in China's province of Fujian, on December 3.

The reason, according to local media, was again a mechanical failure.