A large hole in one of its engines has forced a China Eastern Airlines plane bound for Shanghai to return to Sydney Airport after about an hour in the air.
A spokeswoman for Sydney Airport said Flight MU736 left Sydney about 8.30pm (10.30pm NZT) on Sunday night.
The plane had to turn back an hour after take-off when the hole developed in the engine casing.
China Eastern MU736 Sydney-Shanghai safely returned to SYD after left engine failure. pic.twitter.com/edKRGQCcB6— ChinaAviationReview (@ChinaAvReview) June 11, 2017
Audio purported to be of the pilot's emergency call to Sydney Air Traffic Control has emerged on social media.
Aviation website flight.org posted audio of the pilot telling an air traffic controller: "Engine number one f***ed."
"Sorry, 736. Roger. Any more information," air traffic replies.
"We need to maintain heading," the pilot says.
Firefighters were called to the tarmac to assist the pilots when the plane returned to Sydney.
The Airbus landed safely and no-one was injured during the incident.
Photos of the hole have surfaced on social media and aviation websites.
Engine casing has 'ripped clean off'
Aviation expert Professor Jason Middleton, from the University of New South Wales Aviation School, has described the incident as "a very rare event".
"Remarkable set of photos, most unusual, I've never seen that sort of thing happen before," he said.
"It appears to be on engine one, which is the left engine.
"Looks like the engine casing or cowling has ripped off, forward of the fan - the main initial compressor blade - it's ripped clean off.
"Looks like there's obviously been some preliminary damage in order for that to happen.
"How that might have happened, I'm not sure."
Prof Middleton said the pilots would normally walk around the plane to inspect it before take-off.
"It's quite possible if there was some minor damage that they didn't see," he said.
"At its climbing speed it will be getting faster and faster and that may have been the trigger to rip off some of that engine casing."
Prof Middleton said the aircraft would be able to fly quite comfortably with power from only one engine.