AUDIO from the cockpit of a China Eastern flight that had to return to Sydney airport last night implies the pilot misspoke when alerting the tower.

The Shanghai-bound MU736 flight, which departed Sydney about 8.30pm on Sunday, experienced an engine fault mid-air and returned about an hour after take-off.

In the audio, which has been confirmed by a spokeswoman from China Eastern Airlines, the pilot appears to misspeak when trying to alert authorities to the engine fault.

“Engine number one fooked” can be heard twice in the audio.

“Continue climb to 5000,” the speaker later says.

media_camera The damaged engine on a China Eastern Airlines plane. Picture: AAP Image/Paul Miller

The airline spokeswoman said the audio was a “communication between our flight crew and air traffic control”.

The audio sent social media into a spin, with some suggesting the pilot was trying to say “fault” and others pointing to a slip of the tongue.

“I’ll go with ‘fault’ but amusing all the same,” Dave Monds said of the audio posted to the Facebook page for aviation enthusiasts, Flight.

“Dropping the f-bomb on a new level,” another person posted.

“Well, it got the message across ...” John Bartels wrote.

PHOTO China Eastern Airlines Flight #MU736 (B-6099) engine cowling rips open during climb out from Sydney. (11-JUN-2017). FB Kara Anth pic.twitter.com/D0gR6jEefL — Air Disasters (@AirCrashMayday) June 11, 2017

Photos circulating the web show a huge hole in the engine casing of the Airbus A330, which was forced to circle before touching down safely.

The plane landed in Sydney and passengers, who were put up in hotels, were expected to depart on another flight today.

The returned aircraft is being examined at Sydney airport and an Australian Transport Safety Bureau investigation is underway into the cause of the damage.

China Eastern Airlines General Manager Kathy Zhang confirmed the aircraft was under investigation.

“MU736 (flight) from Sydney to Shanghai encountered an engine problem after take-off,” Ms Zhang said.

“The crew observed the abnormal situation of the left engine and decided to return to Sydney airport immediately. All passengers and crew members were landed safely. They were then arranged accommodation by China Eastern Airlines.”

media_camera A man inspects the damage after a China Eastern Airlines flight was forced to return to Sydney after takeoff after an engine malfunctioned. Picture: 7NEWS

Channel 7’s Sunrise reported residents in the south-west Sydney area of Macarthur reported a low-flying aircraft and “a banging noise” overhead.

“It kind of smelt like burning — oh I was scared, I was really scared. Our group was terrified,” one passenger told the network as her friend added: “Thank God we’re alive.”

Another said: “The Chinese fellow sitting right on the window when we took off — he obviously saw what was going on because he was waving frantically to the staff to come and look at the window.

“There were only about three of four English-speaking people on the plane and the majority of announcements were made in Chinese. That was a little bit tricky.”

China Eastern MU736 Sydney-Shanghai safely returned to SYD after left engine failure. pic.twitter.com/edKRGQCcB6 — ChinaAviationReview (@ChinaAvReview) June 11, 2017

It is believed that members of the cabin crew noticed damage to the air inlet of the left engine — a strip had been torn off the external cover of the engine leaving it partially not contained.

The plane travelled as far south as Bulli when it was forced to radio the problem to Sydney airport, and begin a winding return back over the water before making a hasty landing on the tarmac.

Despite the havoc, passengers applauded airline staff for their professionalism. They were put up in hotels at Sydney airport by China Eastern and are expected to depart Sydney today.

“Today the passengers will be arranged to fly to their destinations on either China Eastern flights or other airlines,” a spokeswoman for the airline said.

media_camera A man inspects the damage after a China Eastern Airlines flight was forced to return to Sydney after takeoff after an engine malfunctioned. Picture: 7NEWS

Meanwhile, Sydney airport was in chaos earlier today as a blanket of fog covered the city this morning, which impacted arrivals and departures.

One international flight has been diverted to Brisbane, and 10 domestic flights were cancelled — a combination of arrivals and departures.

— with AAP