A United Airlines flight traveling from Los Angeles issued a mayday call upon its approach to Sydney International Airport on Thursday, triggering a full-scale emergency response from authorities on the ground.

"We have a full emergency level three for United 787, the sign is UA839, it has low fuel issues and has issued a mayday," New South Wales State Emergency Services announced around 6:00 (AEST).

As a result, state police were forced to close a number of major roads surrounding the airport in case the plane did not make the runway.

But with a number of firetrucks and emergency staff on standby at the tarmac, the Dreamliner did land safely with all 239 passengers on board unharmed.

Despite the initial panic, an Airservices Australia spokesperson explained to the Australian Broadcasting Corporation that instances like this were "not unusual."

Roads around the airport reopened just before 07:00 (AEST).